Esterase EstK from Pseudomonas putida mt‐2: An enantioselective acetylesterase with activity for deacetylation of xylan and poly(vinylacetate)

An extracellular esterase gene estK was identified in Pseudomonas putida mt‐2 and overexpressed at high levels in Escherichia coli. The recombinant EstK enzyme was purified and characterized kinetically against p‐nitrophenyl ester and other aryl–alkyl ester substrates and found to be selective for hydrolysis of acetyl ester substrates with high activity for p‐nitrophenyl acetate (kcat 5.5 Sec−1, KM 285 µM). Recombinant EstK was found to catalyze deacetylation of acetylated beech xylan, indicating a possible in vivo function for this enzyme, and partial deacetylation of a synthetic polymer (poly(vinylacetate)). EstK was found to catalyze enantioselective hydrolysis of racemic 1‐phenylethyl acetate, generating 1R‐phenylethanol with an enantiomeric excess of 80.4%.