Steroid

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Structure of 24-ethyl-lanostane, a hypothetical steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC-approved ring lettering and atom numbering. Trimethyl steroid-nomenclature.svg
Structure of 24-ethyl-lanostane, a hypothetical steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC-approved ring lettering and atom numbering.

A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and as signaling molecules. Hundreds of steroids are found in plants, animals and fungi. All steroids are manufactured in cells from the sterols lanosterol (opisthokonts) or cycloartenol (plants). Lanosterol and cycloartenol are derived from the cyclization of the triterpene squalene. [2]

Contents

The steroid core structure is typically composed of seventeen carbon atoms, bonded in four "fused" rings: three six-member cyclohexane rings (rings A, B and C in the first illustration) and one five-member cyclopentane ring (the D ring). Steroids vary by the functional groups attached to this four-ring core and by the oxidation state of the rings. Sterols are forms of steroids with a hydroxy group at position three and a skeleton derived from cholestane. [1] :1785f [3] Steroids can also be more radically modified, such as by changes to the ring structure, for example, cutting one of the rings. Cutting Ring B produces secosteroids one of which is vitamin D3.

Examples include anabolic steroids, the lipid cholesterol, the sex hormones estradiol and testosterone, [4] :10–19 and the anti-inflammatory drug dexamethasone. [5]

5alpha-Dihydroprogesterone 3D spacefill.png
Space-filling representation
5alpha-Dihydroprogesterone 3D ball.png
Ball-and-stick representation
5α-dihydroprogesterone (5α-DHP), a steroid. The shape of the four rings of most steroids is illustrated (carbon atoms in black, oxygens in red and hydrogens in grey). The nonpolar "slab" of hydrocarbon in the middle (grey, black) and the polar groups at opposing ends (red) are common features of natural steroids. 5α-DHP is an endogenous steroid hormone and a biosynthetic intermediate.

Nomenclature

Gonane, the simplest steroid, consisting only of the common steroid nucleus Gonane.png
Gonane, the simplest steroid, consisting only of the common steroid nucleus
Steroid 5a and 5b stereoisomers 5alpha5betaSteroidIUPAC.png
Steroid 5α and 5β stereoisomers

Gonane, also known as steran or cyclopentanoperhydrophenanthrene, the simplest steroid and the nucleus of all steroids and sterols, [6] [7] is composed of seventeen carbon atoms in carbon-carbon bonds forming four fused rings in a three-dimensional shape. The three cyclohexane rings (A, B, and C in the first illustration) form the skeleton of a perhydro derivative of phenanthrene. The D ring has a cyclopentane structure. When the two methyl groups and eight carbon side chains (at C-17, as shown for cholesterol) are present, the steroid is said to have a cholestane framework. The two common 5α and 5β stereoisomeric forms of steroids exist because of differences in the side of the largely planar ring system where the hydrogen (H) atom at carbon-5 is attached, which results in a change in steroid A-ring conformation. Isomerisation at the C-21 side chain produces a parallel series of compounds, referred to as isosteroids. [8]

Examples of steroid structures are:

In addition to the ring scissions (cleavages), expansions and contractions (cleavage and reclosing to a larger or smaller rings)—all variations in the carbon-carbon bond framework—steroids can also vary:

For instance, sterols such as cholesterol and lanosterol have a hydroxyl group attached at position C-3, while testosterone and progesterone have a carbonyl (oxo substituent) at C-3; of these, lanosterol alone has two methyl groups at C-4 and cholesterol (with a C-5 to C-6 double bond) differs from testosterone and progesterone (which have a C-4 to C-5 double bond).

Cholesterol, a prototypical animal sterol. This structural lipid and key steroid biosynthetic precursor. Colesterol.png
Cholesterol, a prototypical animal sterol. This structural lipid and key steroid biosynthetic precursor.
5a-cholestane, a common steroid core Cholestane.svg
5α-cholestane, a common steroid core

Species distribution and function

In eukaryotes, steroids are found in fungi, animals, and plants.

Fungal steroids

Fungal steroids include the ergosterols, which are involved in maintaining the integrity of the fungal cellular membrane. Various antifungal drugs, such as amphotericin B and azole antifungals, utilize this information to kill pathogenic fungi. [9] Fungi can alter their ergosterol content (e.g. through loss of function mutations in the enzymes ERG3 or ERG6, inducing depletion of ergosterol, or mutations that decrease the ergosterol content) to develop resistance to drugs that target ergosterol. [10] Ergosterol is analogous to the cholesterol found in the cellular membranes of animals (including humans), or the phytosterols found in the cellular membranes of plants. [10] All mushrooms contain large quantities of ergosterol, in the range of tens to hundreds of milligrams per 100 grams of dry weight. [10] Oxygen is necessary for the synthesis of ergosterol in fungi. [10] Ergosterol is responsible for the vitamin D content found in mushrooms; ergosterol is chemically converted into provitamin D2 by exposure to ultraviolet light. [10] Provitamin D2 spontaneously forms vitamin D2. [10] However, not all fungi utilize ergosterol in their cellular membranes; for example, the pathogenic fungal species Pneumocystis jirovecii does not, which has important clinical implications (given the mechanism of action of many antifungal drugs). [10] Using the fungus Saccharomyces cerevisiae as an example, other major steroids include ergosta‐5,7,22,24(28)‐tetraen‐3β‐ol, zymosterol, and lanosterol. [10] S. cerevisiae utilizes 5,6‐dihydroergosterol in place of ergosterol in its cell membrane. [10]

Animal steroids

Animal steroids include compounds of vertebrate and insect origin, the latter including ecdysteroids such as ecdysterone (controlling molting in some species). Vertebrate examples include the steroid hormones and cholesterol; the latter is a structural component of cell membranes that helps determine the fluidity of cell membranes and is a principal constituent of plaque (implicated in atherosclerosis). Steroid hormones include:

Plant steroids

Plant steroids include steroidal alkaloids found in Solanaceae [11] and Melanthiaceae (specially the genus Veratrum), [12] cardiac glycosides, [13] the phytosterols and the brassinosteroids (which include several plant hormones).

Prokaryotes

In prokaryotes, biosynthetic pathways exist for the tetracyclic steroid framework (e.g. in mycobacteria) [14] – where its origin from eukaryotes is conjectured [15] – and the more-common pentacyclic triterpinoid hopanoid framework. [16]

Types

By function

The major classes of steroid hormones, with prominent members and examples of related functions, are:[ citation needed ]

Additional classes of steroids include:

As well as the following class of secosteroids (open-ring steroids):

By structure

Intact ring system

Steroids can be classified based on their chemical composition. [17] One example of how MeSH performs this classification is available at the Wikipedia MeSH catalog. Examples of this classification include:

Cholecalciferol (vitamin D3), an example of a 9,10-secosteroid Cholecalciferol.svg
Cholecalciferol (vitamin D3), an example of a 9,10-secosteroid
Cyclopamine, an example of a complex C-nor-D-homosteroid Cyclopamine.svg
Cyclopamine, an example of a complex C-nor-D-homosteroid
ClassExampleNumber of carbon atoms
Cholestanes Cholesterol27
Cholanes Cholic acid24
Pregnanes Progesterone21
Androstanes Testosterone19
Estranes Estradiol18

In biology, it is common to name the above steroid classes by the number of carbon atoms present when referring to hormones: C18-steroids for the estranes (mostly estrogens), C19-steroids for the androstanes (mostly androgens), and C21-steroids for the pregnanes (mostly corticosteroids). [18] The classification "17-ketosteroid" is also important in medicine.

The gonane (steroid nucleus) is the parent 17-carbon tetracyclic hydrocarbon molecule with no alkyl sidechains. [19]

Cleaved, contracted, and expanded rings

Secosteroids (Latin seco, "to cut") are a subclass of steroidal compounds resulting, biosynthetically or conceptually, from scission (cleavage) of parent steroid rings (generally one of the four). Major secosteroid subclasses are defined by the steroid carbon atoms where this scission has taken place. For instance, the prototypical secosteroid cholecalciferol, vitamin D3 (shown), is in the 9,10-secosteroid subclass and derives from the cleavage of carbon atoms C-9 and C-10 of the steroid B-ring; 5,6-secosteroids and 13,14-steroids are similar. [20]

Norsteroids (nor-, L. norma; "normal" in chemistry, indicating carbon removal) [21] and homosteroids (homo-, Greek homos; "same", indicating carbon addition) are structural subclasses of steroids formed from biosynthetic steps. The former involves enzymic ring expansion-contraction reactions, and the latter is accomplished (biomimetically) or (more frequently) through ring closures of acyclic precursors with more (or fewer) ring atoms than the parent steroid framework. [22]

Combinations of these ring alterations are known in nature. For instance, ewes who graze on corn lily ingest cyclopamine (shown) and veratramine, two of a sub-family of steroids where the C- and D-rings are contracted and expanded respectively via a biosynthetic migration of the original C-13 atom. Ingestion of these C-nor-D-homosteroids results in birth defects in lambs: cyclopia from cyclopamine and leg deformity from veratramine. [23] A further C-nor-D-homosteroid (nakiterpiosin) is excreted by Okinawan cyanobacteriosponges. e.g., Terpios hoshinota, leading to coral mortality from black coral disease. [24] Nakiterpiosin-type steroids are active against the signaling pathway involving the smoothened and hedgehog proteins, a pathway which is hyperactive in a number of cancers.[ citation needed ]

Biological significance

Steroids and their metabolites often function as signalling molecules (the most notable examples are steroid hormones), and steroids and phospholipids are components of cell membranes. [25] Steroids such as cholesterol decrease membrane fluidity. [26] Similar to lipids, steroids are highly concentrated energy stores. However, they are not typically sources of energy; in mammals, they are normally metabolized and excreted.

Steroids play critical roles in a number of disorders, including malignancies like prostate cancer, where steroid production inside and outside the tumour promotes cancer cell aggressiveness. [27]

Biosynthesis and metabolism

Simplification of the end of the steroid synthesis pathway, where the intermediates isopentenyl pyrophosphate (PP or IPP) and dimethylallyl pyrophosphate (DMAPP) form geranyl pyrophosphate (GPP), squalene and lanosterol (the first steroid in the pathway) Sterol synthesis.svg
Simplification of the end of the steroid synthesis pathway, where the intermediates isopentenyl pyrophosphate (PP or IPP) and dimethylallyl pyrophosphate (DMAPP) form geranyl pyrophosphate (GPP), squalene and lanosterol (the first steroid in the pathway)

The hundreds of steroids found in animals, fungi, and plants are made from lanosterol (in animals and fungi; see examples above) or cycloartenol (in other eukaryotes). Both lanosterol and cycloartenol derive from cyclization of the triterpenoid squalene. [2] Lanosterol and cycloartenol are sometimes called protosterols because they serve as the starting compounds for all other steroids.

Steroid biosynthesis is an anabolic pathway which produces steroids from simple precursors. A unique biosynthetic pathway is followed in animals (compared to many other organisms), making the pathway a common target for antibiotics and other anti-infection drugs. Steroid metabolism in humans is also the target of cholesterol-lowering drugs, such as statins. In humans and other animals the biosynthesis of steroids follows the mevalonate pathway, which uses acetyl-CoA as building blocks for dimethylallyl diphosphate (DMAPP) and isopentenyl diphosphate (IPP). [28] [ better source needed ]

In subsequent steps DMAPP and IPP conjugate to form farnesyl diphosphate (FPP), which further conjugates with each other to form the linear triterpenoid squalene. Squalene biosynthesis is catalyzed by squalene synthase, which belongs to the squalene/phytoene synthase family. Subsequent epoxidation and cyclization of squalene generate lanosterol, which is the starting point for additional modifications into other steroids (steroidogenesis). [29] In other eukaryotes, the cyclization product of epoxidized squalene (oxidosqualene) is cycloartenol.

Mevalonate pathway

Mevalonate pathway Mevalonate pathway.svg
Mevalonate pathway

The mevalonate pathway (also called HMG-CoA reductase pathway) begins with acetyl-CoA and ends with dimethylallyl diphosphate (DMAPP) and isopentenyl diphosphate (IPP).

DMAPP and IPP donate isoprene units, which are assembled and modified to form terpenes and isoprenoids [30] (a large class of lipids, which include the carotenoids and form the largest class of plant natural products. [31] Here, the isoprene units are joined to make squalene and folded into a set of rings to make lanosterol. [32] Lanosterol can then be converted into other steroids, such as cholesterol and ergosterol. [32] [33]

Two classes of drugs target the mevalonate pathway: statins (like rosuvastatin), which are used to reduce elevated cholesterol levels, [34] and bisphosphonates (like zoledronate), which are used to treat a number of bone-degenerative diseases. [35]

Steroidogenesis

Human steroidogenesis, with the major classes of steroid hormones, individual steroids and enzymatic pathways. Changes in molecular structure from a precursor are highlighted in white. Steroidogenesis.svg
Human steroidogenesis, with the major classes of steroid hormones, individual steroids and enzymatic pathways. Changes in molecular structure from a precursor are highlighted in white.

Steroidogenesis is the biological process by which steroids are generated from cholesterol and changed into other steroids. [37] The pathways of steroidogenesis differ among species. The major classes of steroid hormones, as noted above (with their prominent members and functions), are the progestogens, corticosteroids (corticoids), androgens, and estrogens. [38] [ citation needed ] Human steroidogenesis of these classes occurs in a number of locations:

Production rates, secretion rates, clearance rates, and blood levels of major sex hormones
SexSex hormoneReproductive
phase
Blood
production rate
Gonadal
secretion rate
Metabolic
clearance rate
Reference range (serum levels)
SI unitsNon-SI units
Men Androstenedione
2.8 mg/day1.6 mg/day2200 L/day2.8–7.3 nmol/L80–210 ng/dL
Testosterone
6.5 mg/day6.2 mg/day950 L/day6.9–34.7 nmol/L200–1000 ng/dL
Estrone
150 μg/day110 μg/day2050 L/day37–250 pmol/L10–70 pg/mL
Estradiol
60 μg/day50 μg/day1600 L/day<37–210 pmol/L10–57 pg/mL
Estrone sulfate
80 μg/dayInsignificant167 L/day600–2500 pmol/L200–900 pg/mL
Women Androstenedione
3.2 mg/day2.8 mg/day2000 L/day3.1–12.2 nmol/L89–350 ng/dL
Testosterone
190 μg/day60 μg/day500 L/day0.7–2.8 nmol/L20–81 ng/dL
Estrone Follicular phase110 μg/day80 μg/day2200 L/day110–400 pmol/L30–110 pg/mL
Luteal phase260 μg/day150 μg/day2200 L/day310–660 pmol/L80–180 pg/mL
Postmenopause40 μg/dayInsignificant1610 L/day22–230 pmol/L6–60 pg/mL
Estradiol Follicular phase90 μg/day80 μg/day1200 L/day<37–360 pmol/L10–98 pg/mL
Luteal phase250 μg/day240 μg/day1200 L/day699–1250 pmol/L190–341 pg/mL
Postmenopause6 μg/dayInsignificant910 L/day<37–140 pmol/L10–38 pg/mL
Estrone sulfate Follicular phase100 μg/dayInsignificant146 L/day700–3600 pmol/L250–1300 pg/mL
Luteal phase180 μg/dayInsignificant146 L/day1100–7300 pmol/L400–2600 pg/mL
Progesterone Follicular phase2 mg/day1.7 mg/day2100 L/day0.3–3 nmol/L0.1–0.9 ng/mL
Luteal phase25 mg/day24 mg/day2100 L/day19–45 nmol/L6–14 ng/mL
Notes and sources
Notes: "The concentration of a steroid in the circulation is determined by the rate at which it is secreted from glands, the rate of metabolism of precursor or prehormones into the steroid, and the rate at which it is extracted by tissues and metabolized. The secretion rate of a steroid refers to the total secretion of the compound from a gland per unit time. Secretion rates have been assessed by sampling the venous effluent from a gland over time and subtracting out the arterial and peripheral venous hormone concentration. The metabolic clearance rate of a steroid is defined as the volume of blood that has been completely cleared of the hormone per unit time. The production rate of a steroid hormone refers to entry into the blood of the compound from all possible sources, including secretion from glands and conversion of prohormones into the steroid of interest. At steady state, the amount of hormone entering the blood from all sources will be equal to the rate at which it is being cleared (metabolic clearance rate) multiplied by blood concentration (production rate = metabolic clearance rate × concentration). If there is little contribution of prohormone metabolism to the circulating pool of steroid, then the production rate will approximate the secretion rate." Sources: See template.

Alternative pathways

In plants and bacteria, the non-mevalonate pathway (MEP pathway) uses pyruvate and glyceraldehyde 3-phosphate as substrates to produce IPP and DMAPP. [30] [41]

During diseases pathways otherwise not significant in healthy humans can become utilized. For example, in one form of congenital adrenal hyperplasia a deficiency in the 21-hydroxylase enzymatic pathway leads to an excess of 17α-Hydroxyprogesterone (17-OHP) – this pathological excess of 17-OHP in turn may be converted to dihydrotestosterone (DHT, a potent androgen) through among others 17,20 Lyase (a member of the cytochrome P450 family of enzymes), 5α-Reductase and 3α-Hydroxysteroid dehydrogenase. [42]

Catabolism and excretion

Steroids are primarily oxidized by cytochrome P450 oxidase enzymes, such as CYP3A4. These reactions introduce oxygen into the steroid ring, allowing the cholesterol to be broken up by other enzymes into bile acids. [43] These acids can then be eliminated by secretion from the liver in bile. [44] The expression of the oxidase gene can be upregulated by the steroid sensor PXR when there is a high blood concentration of steroids. [45] Steroid hormones, lacking the side chain of cholesterol and bile acids, are typically hydroxylated at various ring positions or oxidized at the 17 position, conjugated with sulfate or glucuronic acid and excreted in the urine. [46]

Isolation, structure determination, and methods of analysis

Steroid isolation, depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more [47] or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram. [48] [ page needed ] The methods of isolation to achieve the two scales of product are distinct, but include extraction, precipitation, adsorption, chromatography, and crystallization. In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS, are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample. Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography. [4] :10–19Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity. [48]

Chemical synthesis

Microbial catabolism of phytosterol side chains yields C-19 steroids, C-22 steroids, and 17-ketosteroids (i.e. precursors to adrenocortical hormones and contraceptives). [49] [50] [51] The addition and modification of functional groups is key when producing the wide variety of medications available within this chemical classification. These modifications are performed using conventional organic synthesis and/or biotransformation techniques. [52] [53]

Precursors

Semisynthesis

The semisynthesis of steroids often begins from precursors such as cholesterol, [51] phytosterols, [50] or sapogenins. [54] The efforts of Syntex, a company involved in the Mexican barbasco trade, used Dioscorea mexicana to produce the sapogenin diosgenin in the early days of the synthetic steroid pharmaceutical industry. [47]

Total synthesis

Some steroidal hormones are economically obtained only by total synthesis from petrochemicals (e.g. 13-alkyl steroids). [51] For example, the pharmaceutical Norgestrel begins from methoxy-1-tetralone, a petrochemical derived from phenol.

Research awards

A number of Nobel Prizes have been awarded for steroid research, including:

See also

Related Research Articles

<span class="mw-page-title-main">Cholesterol</span> Sterol biosynthesized by all animal cells

Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol, a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell membranes. When chemically isolated, it is a yellowish crystalline solid.

<span class="mw-page-title-main">Lipid</span> Substance of biological origin that is soluble in nonpolar solvents

In biology and biochemistry, a lipid is a biomolecule that is only soluble in nonpolar solvents. Non-polar solvents are hydrocarbons used to dissolve other hydrocarbon lipid molecules that do not dissolve in water, including fatty acids, waxes, sterols, fat-soluble vitamins, monoglycerides, diglycerides, triglycerides, and phospholipids.

<span class="mw-page-title-main">Progestogen</span> Steroid hormone that activates the progesterone receptor

Progestogens, also sometimes written progestagens or gestagens, are a class of natural or synthetic steroid hormones that bind to and activate the progesterone receptors (PR). Progesterone is the major and most important progestogen in the body. The progestogens are named for their function in maintaining pregnancy, although they are also present at other phases of the estrous and menstrual cycles.

<span class="mw-page-title-main">Antifungal</span> Pharmaceutical fungicide or fungistatic used to treat and prevent mycosis

An antifungal medication, also known as an antimycotic medication, is a pharmaceutical fungicide or fungistatic used to treat and prevent mycosis such as athlete's foot, ringworm, candidiasis (thrush), serious systemic infections such as cryptococcal meningitis, and others. Such drugs are usually obtained by a doctor's prescription, but a few are available over the counter (OTC).

<span class="mw-page-title-main">Ketoconazole</span> Antifungal chemical compound

Ketoconazole, sold under the brand name Nizoral among others, is an antiandrogen and antifungal medication used to treat a number of fungal infections. Applied to the skin it is used for fungal skin infections such as tinea, cutaneous candidiasis, pityriasis versicolor, dandruff, and seborrheic dermatitis. Taken by mouth it is a less preferred option and only recommended for severe infections when other agents cannot be used. Other uses include treatment of excessive hair growth and Cushing's syndrome.

<span class="mw-page-title-main">Ergosterol</span> Chemical compound

Ergosterol (ergosta-5,7,22-trien-3β-ol) is a sterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells. Because many fungi and protozoa cannot survive without ergosterol, the enzymes that synthesize it have become important targets for drug discovery. In human nutrition, ergosterol is a provitamin form of vitamin D2; exposure to ultraviolet (UV) light causes a chemical reaction that produces vitamin D2.

<span class="mw-page-title-main">Squalene</span> Chemical compound

Squalene is an organic compound. With the formula (C5H8)6, it is a triterpene. It is a colourless oil although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as Squalus is a genus of sharks). All plants and animals produce squalene as a biochemical intermediate. An estimated 12% of bodily squalene in humans comes from the sebum. Squalene has a role in topical skin lubrication and protection.

<span class="mw-page-title-main">Sterol</span> Chemical compound

Sterol is an organic compound with formula C
17
H
28
O
, whose molecule is derived from that of gonane by replacement of a hydrogen atom in position 3 by a hydroxyl group. It is therefore an alcohol of gonane. More generally, any compounds that contain the gonane structure, additional functional groups, and/or modified ring systems derived from gonane are called steroids. Therefore, sterols are a subgroup of the steroids. They occur naturally in most eukaryotes, including plants, animals, and fungi, and can also be produced by some bacteria. The most familiar type of animal sterol is cholesterol, which is vital to cell membrane structure, and functions as a precursor to fat-soluble vitamins and steroid hormones.

<i>beta</i>-Sitosterol Chemical compound

β-sitosterol (beta-sitosterol) is one of several phytosterols with chemical structures similar to that of cholesterol. It is a white, waxy powder with a characteristic odor, and is one of the components of the food additive E499. Phytosterols are hydrophobic and soluble in alcohols.

<span class="mw-page-title-main">Triterpene</span> Class of chemical compounds

Triterpenes are a class of chemical compounds composed of three terpene units with the molecular formula C30H48; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi all produce triterpenes, including squalene, the precursor to all steroids.

<span class="mw-page-title-main">Farnesyl-diphosphate farnesyltransferase</span> Class of enzymes

Squalene synthase (SQS) or farnesyl-diphosphate:farnesyl-diphosphate farnesyl transferase is an enzyme localized to the membrane of the endoplasmic reticulum. SQS participates in the isoprenoid biosynthetic pathway, catalyzing a two-step reaction in which two identical molecules of farnesyl pyrophosphate (FPP) are converted into squalene, with the consumption of NADPH. Catalysis by SQS is the first committed step in sterol synthesis, since the squalene produced is converted exclusively into various sterols, such as cholesterol, via a complex, multi-step pathway. SQS belongs to squalene/phytoene synthase family of proteins.

(S)-2,3-Oxidosqualene is an intermediate in the synthesis of the cell membrane sterol precursors lanosterol and cycloartenol, as well as saponins. It is formed when squalene is oxidized by the enzyme squalene monooxygenase. 2,3-Oxidosqualene is the substrate of various oxidosqualene cyclases, including lanosterol synthase, which produces lanosterol, a precursor to cholesterol.

<span class="mw-page-title-main">Lanosterol synthase</span> Mammalian protein found in Homo sapiens

Lanosterol synthase is an oxidosqualene cyclase (OSC) enzyme that converts (S)-2,3-oxidosqualene to a protosterol cation and finally to lanosterol. Lanosterol is a key four-ringed intermediate in cholesterol biosynthesis. In humans, lanosterol synthase is encoded by the LSS gene.

<span class="mw-page-title-main">Ginsenoside</span> Class of steroids

Ginsenosides or panaxosides are a class of natural product steroid glycosides and triterpene saponins. Compounds in this family are found almost exclusively in the plant genus Panax (ginseng), which has a long history of use in traditional medicine that has led to the study of pharmacological effects of ginseng compounds. As a class, ginsenosides exhibit a large variety of subtle and difficult-to-characterize biological effects when studied in isolation.

<span class="mw-page-title-main">Sterol 14-demethylase</span> Class of enzymes

In enzymology, a sterol 14-demethylase (EC 1.14.13.70) is an enzyme of the Cytochrome P450 (CYP) superfamily. It is any member of the CYP51 family. It catalyzes a chemical reaction such as:

In enzymology, a geranyltranstransferase is an enzyme that catalyzes the chemical reaction

<span class="mw-page-title-main">Viridin</span> Chemical compound

Viridin is an antifungal metabolite of Gliocladium virens that was first reported in 1945. Belonging to a class of molecules known as furanosteroids, it has a characteristic highly strained electrophilic furan ring fused between C-4 and C-6 of the steroid framework. Members of this family, including wortmannin, are known to be potent, irreversible covalent inhibitors of phosphoinositide 3-kinases (PI3Ks).

<span class="mw-page-title-main">C-5 sterol desaturase</span>

C-5 sterol desaturase is an enzyme that is highly conserved among eukaryotes and catalyzes the dehydrogenation of a C-5(6) bond in a sterol intermediate compound as a step in the biosynthesis of major sterols. The precise structure of the enzyme’s substrate varies by species. For example, the human C-5 sterol desaturase oxidizes lathosterol, while its ortholog ERG3 in the yeast Saccharomyces cerevisiae oxidizes episterol.

<span class="mw-page-title-main">Oxidosqualene cyclase</span>

Oxidosqualene cyclases (OSC) are enzymes involved in cyclization reactions of 2,3-oxidosqualene to form sterols or triterpenes.

A steroidogenesis inhibitor, also known as a steroid biosynthesis inhibitor, is a type of drug which inhibits one or more of the enzymes that are involved in the process of steroidogenesis, the biosynthesis of endogenous steroids and steroid hormones. They may inhibit the production of cholesterol and other sterols, sex steroids such as androgens, estrogens, and progestogens, corticosteroids such as glucocorticoids and mineralocorticoids, and neurosteroids. They are used in the treatment of a variety of medical conditions that depend on endogenous steroids.

References

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