Molecular characterisation of the gene encoding an esterase from Bacillus licheniformis sharing significant similarities with lipases

An esterase gene from the moderate thermophilic strain Bacillus licheniform is LCB40 was cloned and expressed in Escherichia coli. Comparison of the am ino acid sequence of the esterase with those of known lipases and esterases showed the presence of the well-conserved Gly-X-Ser-X-Gly pentapeptide, wi th an alanine replacing the first glycine. This substitution has never been reported for an esterase but it is present in the lipases from Bacillus su btilis, Bacillus pumilus and Galactomyces candidum. The amino acid sequence showed similarities with lipases and with mammalian lecithin-cholesterol a cyltranferases and no similarities with esterases. The enzyme activity of a crude extract from a recombinant Escherichia coli strain showed hydrolysis of p-nitrophenyl caprylate (pNPC8) as for esterases, but not of p-nitrophe nyl palmitate (pNPC16) or olive oil such as for lipases. Thus, the enzyme d isplays the original property of associating the activity of an esterase wi th a primary sequence showing high similarity with lipases.