Identification of Novel Esterase from Metagenomic Library of Yangtze River

A metagenomic library of surface-water microbes from the Yangtze River in China was constructed, and a novel esterase, designated as EstY, was isolated and characterized. EstY had 423 amino acids with an estimated molecular mass of 44 kDa and pI of 7.28. It hydrolyzed various p-nitrophenyl esters (acetate, butyrate, caprate, caprylate, laurate, myristate, and palmitate) and its best substrate was p-nitrophenyl caprate (C8). The optimum pH for EstY activity was 9.0 and the optimum temperature was 50 degrees C. Metal ions, such as Mn2+, Co2+, Hg2+, Zn2+, and Fe3+, strongly inhibited the activity of EstY, whereas Mg2+ was required for maximal activity. Activity remained in the presence of 10% alcohol, acetone, isopropanol, and dimethyl sulfoxide, respectively. An analysis of the amino acid sequence deduced from estY revealed that it had 7 closely related lipolytic enzymes. Moreover, a sequence analysis showed that EstY, like its 7 relatives, did not belong to any known lipolytic enzyme family.