Purification and characterization of a carboxylesterase from Pseudomonas sp. KWI-56

An intracellular carboxylesterase from Pseudomonas sp. was overproduced in E. coli, and purified to homogeneity by a combination of hydrogen bond chromatography, gel filtration, and hydrophobic interaction chromatography. Gel filtration and SDS-PAGE suggested that the purified enzyme consisted of two subunits of molecular mass of 28 kDa. Its isoelectric point was 5.9. The enzyme was thermolabile, and showed its maximum activity at 22 degrees C (pH 7.5). Methyl propionate was hydrolyzed at the highest rate among the fatty acid methyl esters tested. PMSF, DFP, PCMB, and HgCl2 inhibited the enzyme markedly, suggesting that serine and/or cysteine is in or near the active site.