BioH

Family: BioH

Block: X

Parent Family: Abhydrolase_6

Comment

Pimelyl-[acyl-carrier protein] methyl ester esterase: BioH family previously included in AlphaBeta_hydrolase family. The structure of ecoli-bioh by Sanishvili et al pdb:1M33 allowed description of function of this family. This CoA-binding enzyme is required for the production of pimeloyl-coenzyme A, the substrate of the BioF protein early in the biosynthesis of biotin. Its exact function is unknown. Members of this family are restricted to the proteobacteria. BioH shows carboxylesterase activity with a preference for short chain fatty acid esters (acyl chain length of up to 6 carbons). It also displays a weak thioesterase activity. Biotin synthesis necessitate the fatty acid synthetic pathway: Malonyl-thioester is methylated by BioC, which allows recognition of this atypical substrate by the fatty acid synthetic enzymes. The malonyl-thioester methyl ester enters fatty acid synthesis as the primer and undergoes two reiterations of the fatty acid elongation cycle to give pimeloyl-acyl carrier protein (ACP) methyl ester, which is hydrolyzed to pimeloyl-ACP and methanol by BioH. In Pseudomonas aeruginosa the bioH gene is within a biotin synthesis operon and its transcription is coregulated with the other biotin operon genes. In Escherichia coli the gene is not located within a biotin synthetic operon and its transcription is not coregulated with the other biotin synthesis genes (Cao et al. 2017). In Francisella BioJ is the enzyme of the biotin biosynthesis pathway that determines the chain length of the biotin valeryl side-chain. It is the functionnal equivalent of BioH although it shows low homology to BioH (belongs to hormone sensitive lipase family)( Feng et al. 2014). In Haemophilus influenzae it is another family Duf_452 which plays the role (Shi et al. 2016). In Helicobacter it is another alpha/beta hydrolase BioV (Bi et al. 2016)