Deoxyribose 5-Phosphate Aldolase
II. PURIFICATION AND PROPERTIES OF THE RAT LIVER ENZYME
D. P. Groth 1
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1 From the Departments of Biochemistry and Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
Deoxyribose 5-phosphate aldolase was purified about 2000-fold from rat liver by ammonium sulfate fractionation and diethylaminoethyl cellulose and hydroxylapatite chromatography. The purified enzyme was free of triosephosphate isomerase. The Michaelis-Menten constants for acetaldehyde, d-glyceraldehyde 3-phosphate, and 2-deoxy-d-ribose 5-phosphate were found to be 2.67 x 10-4 m, 2.0 x 10-4 m, and 1.7 x 10-4 m, respectively. The equilibrium constant for the aldolase-catalyzed reaction was approximately 2 to 3 x 10-4 at pH 7.5 and 22°.
The purified enzyme preparations were essentially inactive in the absence of a carboxylate ion activator such as citrate. Half-maximal activation of the enzyme by citrate, succinate, and glutarate occurred at 1 x 10-4 m, 2 x 10-4 m, and 5 x 10-4 m, respectively. The molecular weight of the purified enzyme was estimated to be 253,000 by sucrose density gradient techniques. Although the enzyme showed a marked tendency to aggregate to form a dimer and trimer, the presence of an activating carboxylate ion did not influence the observed aggregation.
Submitted on November 1, 1965
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