Nucleoside diphosphatase from pig liver: Purification and some properties

Abstract

A procedure is described for purification of nucleoside diphosphatase from pig liver microsomes which avoids exposure of the enzyme to potentially denaturing conditions. The purest fractions obtained have specific activities of approximately 100 units/mg and appear to contain approximately 35% NDPase on a protein basis. Pig liver nucleoside diphosphatase resembles the enzyme obtained from other mammalian tissues in its substrate specificity and in its interaction with MgATP 2− as an allosteric modifier. However the molecular weight of the pig liver enzyme appears higher than that reported for other nucleoside diphosphatases, and activation by MgATP 2− is attributable to an increase in the maximal rate of nucleoside diphosphate hydrolysis rather than to a decrease in K m . These differences in properties seem to be due to a species difference since similar properties were found with pig liver enzyme prepared by a different extraction procedure. The kinetic parameters which describe the reaction catalyzed by pig liver nucleoside diphosphatase are insensitive to changes in [H +]over the range pH 6.5–8.6. The intracellular location of nucleoside diphosphatase is microsomal in both pig and chicken liver.