Comparative properties of yeast and muscle aldolase.

Aldolases derived from various sources may be conveniently segregated into two types on the basis of the effect of metalchelating agents on their catalytic activity (1). For example, the activity of highly purified yeast aldolase (type II) is inhibited by chelating agents, and contains zinc apparently as an integral part of the enzyme. It has also been shown that this enzyme is specifically activated by potassium ions (2). On the other hand, the activity of muscle aldolase (type I) is indifferent to chelating agents, does not contain significant quantities of divalent metal ions, and is not activated by potassium ions (2). It is conceivable that the differences noted are reflections of distinctive active sites or, alternatively, only dissimilarities in the over-all structure of the molecules, the active sites remaining essentially equivalent. A more comprehensive analysis of the catalytic properties of yeast and muscle aldolase should resolve this question. In the present report it is shown that the muscle and yeast enzyme have characteristically different specificities, pH profiles, temperature dependence, and response to the action of carboxypeptidase.