Abstract
Phosphodiesterase was isolated from the lyophilized venom of Agkistrodon acutus from China using gel filtration on a Sephadex G-75 column, followed by chromatography on diethylaminoethyl (DEAE) -Sephadex A-50, carboxymethyl (CM) -Cellulose and Affi-Gel Blue affinity. Homogeneity was established by the formation of a single band in acrylamide gel electrophoresis, isoelectric focusing, sodium dodecyl sulfate (SDS) acrylamide gel electrophoresis and immunodiffusion. Phosphodiesterase activity was inhibited by ethylenediamine tetraacetic acid (EDTA), ethyleneglycol (β-aminoethyl) N, N, N', N'-tetraacetic acid (EGTA), o-phenanthroline, cysteine, thioglycolic acid, glutathione or p-chloromercuribenzoate (PCMB) but not by soybean trypsin inhibitor (SBTI), limabean trypsin inhibitor (LBTI), egg white trypsin inhibitor (EWTI), benzamidine or trasylol. The molecular weight of this enzyme was determined to be approximately 140, 000 and the isoelectric point was found to be pH 7.4 by isoelectric focusing with carrier ampholyte. The phosphodiesterase activity of the final preparation was 2, 190 units/mg. This protein was unstable to heat treatment and stable between. pH 7 and 12. Its michaelis constant (Km) and inhibition constant (Ki) values for pnitrophenyl thymidine-5'-phosphate or EDTA were found to be 1.6×10-3M and 5.8×10-6M, respectively. This protein did not contain any carbohydrates.
