Ox liver carboxylesterase has been reproducibly purified on a large scale from an acetone powder. The enzyme, while significantly purified, is not electrophoretically homogeneous and consists of three major proteins, here called electrophoretic variants 1, 2, and 3. All three variants are very similar protein
Chicken, sheep, and horse liver carboxylesterases have been purified by procedures involving ammonium sulfate fractionation, ion-exchange chromatography and gel filtration on Sephadex. The actual yields of the procedures described were as follows: chicken, 1 g from 2 kg of liver powder (chloroform-acetone); sheep, 200 mg from 400 g of powder (chloroform-acetone); horse, 230 mg from 800 g of powder (acetone). The purified enzymes are free of non-carboxyl-esterase protein as shown by gel electrophoresis, although they do contain electrophoretic variants. The equivalent weight of the chicken enzyme is 67,000 based on titration with p-nitrophenyl diethyl phosphate or bis(p-nitrophenyl) phosphate, whereas those of the sheep and horse enzymes are similar to 69,500 and similar to 70,000, respectively, based on titration with p-nitrophenyl dimethylcarbamate.
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 approximately 50 mg from 530 g of chloroform-acetone powder. The preparation is electrophoretically homogeneous. Active-site titrations with paraoxon gave an equivalent weight of approximately 83 000. The molecular weight, found from sedimentation equilibrium experiments, is approximately 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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.