Vitamin K is a family of structurally similar, fat-soluble vitamers found in foods and marketed as dietary supplements. The human body requires vitamin K for post-synthesis modification of certain proteins that are required for blood coagulation or for controlling binding of calcium in bones and other tissues. The complete synthesis involves final modification of these so-called "Gla proteins" by the enzyme gamma-glutamyl carboxylase that uses vitamin K as a cofactor.
Biosynthesis, i.e., chemical synthesis occurring in biological contexts, is a term most often referring to multi-step, enzyme-catalyzed processes where chemical substances absorbed as nutrients serve as enzyme substrates, with conversion by the living organism either into simpler or more complex products. Examples of biosynthetic pathways include those for the production of amino acids, lipid membrane components, and nucleotides, but also for the production of all classes of biological macromolecules, and of acetyl-coenzyme A, adenosine triphosphate, nicotinamide adenine dinucleotide and other key intermediate and transactional molecules needed for metabolism. Thus, in biosynthesis, any of an array of compounds, from simple to complex, are converted into other compounds, and so it includes both the catabolism and anabolism of complex molecules. Biosynthetic processes are often represented via charts of metabolic pathways. A particular biosynthetic pathway may be located within a single cellular organelle, while others involve enzymes that are located across an array of cellular organelles and structures.
Phytomenadione, also known as vitamin K1 or phylloquinone, is a vitamin found in food and used as a dietary supplement. It is on the World Health Organization's List of Essential Medicines.
Menatetrenone (INN), also known as menaquinone-4 (MK-4), is one of the nine forms of vitamin K2.
The acetolactate synthase (ALS) enzyme is a protein found in plants and micro-organisms. ALS catalyzes the first step in the synthesis of the branched-chain amino acids.
In molecular biology, Beta-ketoacyl-ACP synthase EC 2.3.1.41, is an enzyme involved in fatty acid synthesis. It typically uses malonyl-CoA as a carbon source to elongate ACP-bound acyl species, resulting in the formation of ACP-bound β-ketoacyl species such as acetoacetyl-ACP.
The crotonase family comprises mechanistically diverse proteins that share a conserved trimeric quaternary structure, the core of which consists of 4 turns of a (beta/beta/alpha)n superhelix.
Isochorismate synthase ( EC 5.4.4.2) is an isomerase enzyme that catalyzes the first step in the biosynthesis of vitamin K2 (menaquinone) in Escherichia coli.
The enzyme aminocyclopropane-1-carboxylic acid synthase catalyzes the synthesis of 1-Aminocyclopropane-1-carboxylic acid (ACC), a precursor for ethylene, from S-Adenosyl methionine, an intermediate in the Yang cycle and activated methyl cycle and a useful molecule for methyl transfer:
4-amino-4-deoxychorismate lyase is an enzyme that participates in folate biosynthesis by catalyzing the production of PABA by the following reaction
The enzyme 1,4-dihydroxy-2-naphthoyl-CoA synthase catalyzes the sixth step in the biosynthesis of phylloquinone and menaquinone, the two forms of vitamin K. In E. coli, 1,4-dihydroxy-2-naphthoyl-CoA synthase, formerly known as naphthoate synthase, is encoded by menB and uses O-succinylbenzoyl-CoA as a substrate and converts it to 1,4-dihydroxy-2-naphthoyl-CoA.
o-Succinylbenzoate—CoA ligase, encoded from the menE gene in Escherichia coli, catalyzes the fifth reaction in the synthesis of menaquinone. This pathway is called 1, 4-dihydroxy-2-naphthoate biosynthesis I. Vitamin K is a quinone that serves as an electron transporter during anaerobic respiration. This process of anaerobic respiration allows the bacteria to generate the energy required to survive.
In molecular biology, the protein domain SAICAR synthase is an enzyme which catalyses a reaction to create SAICAR. In enzymology, this enzyme is also known as phosphoribosylaminoimidazolesuccinocarboxamide synthase. It is an enzyme that catalyzes the chemical reaction
In enzymology, a cystathionine gamma-synthase is an enzyme that catalyzes the formation of cystathionine from cysteine and an activated derivative of homoserine, e.g.:
In enzymology, SEPHCHC synthase (EC EC 2.2.1.9), encoded by menD gene in E. coli, is an enzyme that catalyzes the second step of menaquinone (vitamin K2) biosynthesis. The two substrates of this enzyme are 2-oxoglutarate and isochorismate. The products of this enzyme are 5-enolpyruvoyl-6-hydroxy-2-succinyl-cyclohex-3-ene-1-carboxylate and CO2. It belongs to the transferase family.
1-4-dihydroxy-2-napthoate (DHNA) polyprenyltransferase (EC 2.5.1.74)is an enzyme that catalyzes the chemical reaction: all-trans-nonaprenyl diphosphate + 1-4-dihydroxy-2-napthoate + H+ demethylmenaquinol-9 + diphosphate + carbon dioxide
The enzyme 1,4-dihydroxy-2-naphthoyl-CoA hydrolase (EC 3.1.2.28; systematic name 1,4-dihydroxy-2-naphthoyl-CoA hydrolase) catalyses the following reaction:
o-Succinylbenzoate synthase (OSBS) (EC 4.2.1.113) is an enzyme encoded by the menC gene in E.coli, and catalyzes the dehydration of 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (SHCHC) to form 4-(2'-carboxyphenyl)-4-oxobutyrate, also called o-succinylbenzoate or OSB, hence the name of the enzyme. This reaction is the fourth step in the menaquinone biosynthetic pathway, which is used by bacteria to synthesize menaquinone, also known as vitamin K2.
Ketoacyl synthases (KSs) catalyze the condensation reaction of acyl-CoA or acyl-acyl ACP with malonyl-CoA to form 3-ketoacyl-CoA or with malonyl-ACP to form 3-ketoacyl-ACP. This reaction is a key step in the fatty acid synthesis cycle, as the resulting acyl chain is two carbon atoms longer than before. KSs exist as individual enzymes, as they do in type II fatty acid synthesis and type II polyketide synthesis, or as domains in large multidomain enzymes, such as type I fatty acid synthases (FASs) and polyketide synthases (PKSs). KSs are divided into five families: KS1, KS2, KS3, KS4, and KS5.
Coenzyme Q5, methyltransferase, more commonly known as COQ5, is an enzyme involved in the electron transport chain. COQ5 is located within the mitochondrial matrix and is a part of the biosynthesis of ubiquinone.
