LINGCOD MUSCLE PHOSPHORIBOISOMERASE AND RIBULOSE 5′-PHOSPHATE 3′-EPIMERASE

Abstract

Comparatively pure phosphoriboisomerase and ribulose 5′-phosphate 3′-epimerase enzyme preparations were obtained from lingcod muscle by a simple procedure involving water extraction, saturation of the extract with ammonium sulphate, dialysis, brief heating to 55 °C, lyophilization of the solution, and final separation by ion exchange chromatography, using diethylamiuoethyl cellulose columns. Both enzymes have broad pH optima above pH 7.0, but are rapidly inactivated below this value. The following equilibria were established and compared with those obtained by other investigators: [Formula: see text], 1.35:1.0; [Formula: see text], 1: 1.5 and [Formula: see text], 1:0.58:0.66. The ketopentulose phosphate resulting from the action of phosphoriboisomerase on D-ribose 5-phosphate was isolated and identified as D-ribulose5-phosphate. Both D-ribulose and D-xylulose were demonstrated after subjecting a product of epimerase action to hydrolysis by acid phosphatase and ion exchange chromatography.