Hydroperoxide lyase

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Hydroperoxide lyase
Identifiers
EC number 4.2.99.-
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum

Hydroperoxide lyases are enzymes that catalyze the cleavage of C-C bonds in the hydroperoxides of fatty acids. They belong to the cytochrome P450 enzyme family (CYP74C and CYP74B). [1]

Polyunsaturated fatty acids such as linolenic and linoleic acids are susceptible to formation of hydroperoxides upon contact with oxygen in air. Hydroperoxides are highly reactive functional groups since they contain an oxidant (O-O bond) adjacent to a reductant (C-H bonds). When flanked by olefins, the hydroperoxides can be induced to rearrange to give the hemiacetal. It is this reaction that is catalyzed by hydroperoxide lyases. The resulting aldehydes are notable as fragrances, green leaf volatiles, and antifeedants. [2]

An illustrative transformation involving a hydroperoxide lyase. Here cis-3-hexenal is generated by conversion of linolenic acid to the hydroperoxide by the action of a lipoxygenase followed by the lyase-induced formation of the hemiacetal. LyaseNonenalHemiAc.png
An illustrative transformation involving a hydroperoxide lyase. Here cis-3-hexenal is generated by conversion of linolenic acid to the hydroperoxide by the action of a lipoxygenase followed by the lyase-induced formation of the hemiacetal.

Related Research Articles

Cytochrome P450 Class of enzymes

Cytochromes P450 (CYPs) are a superfamily of enzymes containing heme as a cofactor that function as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various compounds, as well as for hormone synthesis and breakdown. In plants, these proteins are important for the biosynthesis of defensive compounds, fatty acids, and hormones.

CYP2E1

Cytochrome P450 2E1 is a member of the cytochrome P450 mixed-function oxidase system, which is involved in the metabolism of xenobiotics in the body. This class of enzymes is divided up into a number of subcategories, including CYP1, CYP2, and CYP3, which as a group are largely responsible for the breakdown of foreign compounds in mammals.

Lipoxygenase

Lipoxygenases are a family of (non-heme) iron-containing enzymes most of which catalyze the dioxygenation of polyunsaturated fatty acids in lipids containing a cis,cis-1,4- pentadiene into cell signaling agents that serve diverse roles as autocrine signals that regulate the function of their parent cells, paracrine signals that regulate the function of nearby cells, and endocrine signals that regulate the function of distant cells.

Any enzyme system that includes cytochrome P450 protein or domain can be called a P450-containing system.

CYP2C8

Cytochrome P4502C8 (abbreviated CYP2C8), a member of the cytochrome P450 mixed-function oxidase system, is involved in the metabolism of xenobiotics in the body. Cytochrome P4502C8 also possesses epoxygenase activity, i.e. it metabolizes long-chain polyunsaturated fatty acids, e.g. arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and Linoleic acid to their biologically active epoxides.

CYP17A1

Cytochrome P450 17A1, also called steroid 17α-monooxygenase, 17α-hydroxylase, 17,20-lyase, or 17,20-desmolase, is an enzyme of the hydroxylase type that in humans is encoded by the CYP17A1 gene on chromosome 10. It is ubiquitously expressed in many tissues and cell types, including the zona reticularis and zona fasciculata of the adrenal cortex as well as gonadal tissues. It has both 17α-hydroxylase and 17,20-lyase activities, and is a key enzyme in the steroidogenic pathway that produces progestins, mineralocorticoids, glucocorticoids, androgens, and estrogens. More specifically, the enzyme acts upon pregnenolone and progesterone to add a hydroxyl (-OH) group at carbon 17 position (C17) of the steroid D ring, or acts upon 17α-hydroxyprogesterone and 17α-hydroxypregnenolone to split the side-chain off the steroid nucleus.

CYP2C18

Cytochrome P450 2C18 is a protein that in humans is encoded by the CYP2C18 gene.

CYP4A11

Cytochrome P450 4A11 is a protein that in humans is codified by the CYP4A11 gene.

CYP4F2

Leukotriene-B(4) omega-hydroxylase 1 is an enzyme involved in the metabolism various endogenous substrates and xenobiotics. Most notable substrate of the enzyme is leukotriene B4, a potent mediator of inflammation. The enzyme is encoded by the CYP4F2 gene in humans.

CYP4F8

Cytochrome P450 4F8 is a protein that in humans is encoded by the CYP4F8 gene.

CYP4F12

Cytochrome P450 4F12 is a protein that in humans is encoded by the CYP4F12 gene.

CYP4F3

Leukotriene-B(4) omega-hydroxylase 2 is an enzyme that in humans is encoded by the CYP4F3 gene. CYP4F3 encodes two distinct enzymes, CYP4F3A and CYP4F3B, which originate from the alternative splicing of a single pre-mRNA precursor molecule; selection of either isoform is tissue-specific with CYP3F3A being expressed mostly in leukocytes and CYP4F3B mostly in the liver.

CYP4F22

CYP4F22 is a protein that in humans is encoded by the CYP4F22 gene.

CYP4F11

CYP4F11 is a protein that in humans is encoded by the CYP4F11 gene. This gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. This gene is part of a cluster of cytochrome P450 genes on chromosome 19. Another member of this family, CYP4F2, is approximately 16 kb away. Alternatively spliced transcript variants encoding the same protein have been found for this gene.

CYP4A22

CYP4A22 also known as fatty acid omega-hydroxylase is a protein which in humans is encoded by the CYP4A22 gene.

Oxylipin

Oxylipins constitute a family of oxygenated natural products which are formed from fatty acids by pathways involving at least one step of dioxygen-dependent oxidation. Oxylipins are derived from polyunsaturated fatty acids (PUFAs) by COX enzymes (cyclooxygenases), by LOX enzymes (lipoxygenases), or by cytochrome P450 epoxygenase.

Fatty-acid peroxygenase is an enzyme with systematic name fatty acid:hydroperoxide oxidoreductase (RH-hydroxylating). This enzyme catalyses the following chemical reaction

Epoxydocosapentaenoic acid

Epoxide docosapentaenoic acids are metabolites of the 22-carbon straight-chain omega-3 fatty acid, docosahexaenoic acid (DHA). Cell types that express certain cytochrome P450 (CYP) epoxygenases metabolize polyunsaturated fatty acid's (PUFAs) by converting one of their double bonds to an epoxide. In the best known of these metabolic pathways, cellular CYP epoxygenases metabolize the 20-carbon straight-chain omega-6 fatty acid, arachidonic acid, to epoxyeicosatrienoic acids (EETs); another CYP epoxygenase pathway metabolizes the 20-carbon omega-3 fatty acid, eicosapentaenoic acid (EPA), to epoxyeicosatetraenoic acids (EEQs). CYP epoxygenases similarly convert various other PUFAs to epoxides These epoxide metabolites have a variety of activities. However, essentially all of them are rapidly converted to their corresponding, but in general far less active, Vicinal (chemistry) dihydroxy fatty acids by ubiquitous cellular Soluble epoxide hydrolase. Consequently, these epoxides, including EDPs, operate as short-lived signaling agents that regulate the function of their parent or nearby cells. The particular feature of EDPs distinguishing them from EETs is that they derive from omega-3 fatty acids and are suggested to be responsible for some of the beneficial effects attributed to omega-3 fatty acids and omega-3-rich foods such as fish oil.

Epoxyeicosatetraenoic acids are a set of biologically active epoxides that various cell types make by metabolizing the omega 3 fatty acid, eicosapentaenoic acid (EPA), with certain cytochrome P450 epoxygenases. These epoxygenases can metabolize EPA to as many as 10 epoxides that differ in the site and/or stereoisomer of the epoxide formed; however, the formed EEQs, while differing in potency, often have similar bioactivities and are commonly considered together.

Cytochrome P450 omega hydroxylases, also termed cytochrome P450 ω-hydroxylases, CYP450 omega hydroxylases, CYP450 ω-hydroxylases, CYP omega hydroxylase, CYP ω-hydroxylases, fatty acid omega hydroxylases, cytochrome P450 monooxygenases, and fatty acid monooxygenases, are a set of cytochrome P450-containing enzymes that catalyze the addition of a hydroxyl residue to a fatty acid substrate. The CYP omega hydroxylases are often referred to as monoxygenases; however, the monooxygenases are CYP450 enzymes that add a hydroxyl group to a wide range of xenobiotic and naturally occurring endobiotic substrates, most of which are not fatty acids. The CYP450 omega hydroxylases are accordingly better viewed as a subset of monooxygenases that have the ability to hydroxylate fatty acids. While once regarded as functioning mainly in the catabolism of dietary fatty acids, the omega oxygenases are now considered critical in the production or break-down of fatty acid-derived mediators which are made by cells and act within their cells of origin as autocrine signaling agents or on nearby cells as paracrine signaling agents to regulate various functions such as blood pressure control and inflammation.

References

  1. Grechkin AN, Brühlmann F, Mukhtarova LS, Gogolev YV, Hamberg M (2006). "Hydroperoxide lyases (CYP74C and CYP74B) catalyze the homolytic isomerization of fatty acid hydroperoxides into hemiacetals". Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids. 1761 (12): 1419–28. doi:10.1016/j.bbalip.2006.09.002. PMID   17049304.
  2. Matsui K (2006). "Green leaf volatiles: hydroperoxide lyase pathway of oxylipin metabolism". Current Opinion in Plant Biology. 9 (3): 274–80. doi:10.1016/j.pbi.2006.03.002. PMID   16595187.

Further reading