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.EXPERIMENTAL PROCEDURE Chemicals-The crystalline cyclohexylamine sulfate salt of fructose-di-P was prepared (3) from a sample of dibarium fructose-di-P procured from Schwarz BioResearch Inc. Sorbose-1-P and sorbose-1,6-diphosphate were kindly supplied by Dr. Henry A. Lardy.Fructose-l-P was cordially supplied by Dr. Carl S. Vestlmg; in addition, this compound was obtained from Sigma Chemical Company.Fructose-6-P was obtained from Schwarz BioResearch, Inc.The barium salts of the above compounds were converted to the sodium salts by treatment with Dowex 50-H+, followed by neutralization with NaHCOa.In the experiments reported, the D isomer of glyceraldehyde-3-P was used exclusively.Samples of n-glyceraldehyde-3-P as well as dihydroxyacetone-P were graciously donated by Dr. Clinton Ballou; in addition, these compounds were synthesized according to the procedures of Ballou and Fischer (4, 5).The products obtained compared favorably with the published analysis; in particular, there was no detectable contamination of glyceraldehyde-3-P with dihydroxyacetone-P or vice versa.Acetol phosphate was synthesized by an independently developed procedure resembling that recently reported by Sellinger and Miller (6).The sources of other compounds employed has been cited (2).