The purification and properties of rabbit-muscle myokinase

Abstract

The preparation of myokinase, homogenous by electrophoretic and ultracentrifugal analysis and of constant specific activity is described. Pure myokinase is very readily oxidized by exposure to glass or cellophane; such treatment predisposes the enzyme to denaturation. The reactivation of the oxidized enzyme with cysteine shows that the enzyme contains highly reactive sulfhydryl groups. Protection of the sulfhydryl groups with cysteine, or other sulfhydryl-containing proteins, endows the enzyme with considerable stability to heating and acid conditions. Titration of the sulfhydryl groups of myokinase indicated that the enzyme possesses 2 groups/molecule. A molecular weight of 21,600 is postulated. Ultracentrifuge studies indicated that myokinase does not polymerize on oxidation.