| Pathway Id | ko00780 |
| Class & Sub-Class | Class: Metabolism Sub-Class: Metabolism of cofactors and vitamins |
| Description | Biotin (vitamin H or vitamin B7) is the essential cofactor of biotin-dependent carboxylases; such as pyruvate carboxylase and acetyl-CoA carboxylase. Mammals cannot synthesize biotin; while in bacteria; fungi; and plants it is synthesized from pimelate thioester through different pathways. In E. coli and many organisms; pimelate thioester is derived from malonyl-ACP. The pathway starts with the methylation to malonyl-ACP methyl ester; followed by the fatty acid chain elongation cycle to form pimeloyl-ACP methyl ester; which is then demethylated to form pimeloyl-ACP [MD:M00572]. Pimeloyl-ACP is converted to biotin through the final four steps in the biotin bicyclic ring assembly; which are conserved among biotin-producing organisms [MD:M00123]. In B. subtilis; biotin is derived from pimeloyl-ACP formed by oxidative cleavage of long-chain acyl-ACPs [MD:M00573]. Some bacteria synthesize biotin from pimeloyl-CoA derived from pimelate [MD:M00577]. Biotin is covalently attached to biotin-dependent carboxylase by biotin protein ligase; also known as holocarboxylase synthase in mammals; to form an active holocarboxylase. After degradation of the biotinylated carboxylase into biocytin; it is further degraded by biotinidase to release free biotin; which is recycled in holocarboxylase synthesis. Biotin is catabolized by beta-oxidation of the valeric acid side chain or oxidation of sulfur in the heterocyclic ring. Source: KEGG Database |
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