Purification and properties of a carboxylesterase from the liver of tiger shark (Galeocerdo cuvier)

Abstract

A procedure is described for the purification of a carboxylesterase from shark liver, using a chloroform-acetone powder prepared from the liver as the starting material. The yield of purified enzyme is ~50 mg from 530 g of chloroform–acetone powder. The preparation is electrophoretically homogeneous. Active-site titrations with paraoxon gave an equivalent weight of ~83 000. The molecular weight, found from sedimentation equilibrium experiments, is ~80 000. There is no evidence of any association or dissociation of this species. The enzyme shows a marked preference for aryl esters over alkyl esters, in contrast to other carboxylesterases so far studied. The amino acid composition of the purified enzyme is reported.