The physiological role of BioH is to remove the methyl group introduced by BioC when the pimeloyl moiety is complete. It allows to synthesize pimeloyl-ACP via the fatty acid synthetic pathway through the hydrolysis of the ester bonds of pimeloyl-ACP esters. E.coli employs a methylation and demethylation strategy to allow elongation of a temporarily disguised malonate moiety to a pimelate moiety by the fatty acid synthetic enzymes. BioH shows a preference for short chain fatty acid esters (acyl chain length of up to 6 carbons) and short chain p-nitrophenyl esters. Also displays a weak thioesterase activity. Can form a complex with CoA, and may be involved in the condensation of CoA and pimelic acid into pimeloyl-CoA, a precursor in biotin biosynthesis. Catalyzes the hydrolysis of the methyl ester bond of dimethylbutyryl-S-methyl mercaptopropionate (DMB-S-MMP) to yield dimethylbutyryl mercaptopropionic acid (DMBS-MPA) during the biocatalytic conversion of simvastin acid from monacolin J acid. Can also use acyl carriers such as dimethylbutyryl-S-ethyl mercaptopropionate (DMB-S-EMP) and dimethylbutyryl-S-methyl thioglycolate (DMB-S-MTG) as the thioester substrates. 6-carboxyhexanoyl-[ACP] methyl ester + H2O = 6-carboxyhexanoyl-[ACP] + H(+) + methanol Strongly inhibited by phenylmethylsulfonyl fluoride (PMSF). The highest catalytic efficiency was observed with pNP-acetate, then with pNP-propionate, pNP-butyrate and pNP-caproate. Optimum pH is 8.0-8.5. The activity is more than 90% in the pH range from 7 to 9. Optimum temperature is between 20 and 30 degrees Celsius. Cofactor biosynthesis; biotin biosynthesis. Monomer. Cells display no detectable hydrolysis of the thioester and no trace of DMB-S-MPA. Belongs to the AB hydrolase superfamily. Carboxylesterase BioH family.