Ribulose-1 ,5-P, labelled with tritium in the C-3 position was converted to 2 moles of phosphoglyceric acid by the carboxydismutase. Over 98 Olio of the radioactivity was found in the water, less than 0.1 being in phosphoglyceric acid, indicating that the proton lost from the 3 position of the substrate does not contribute to the formation of product. The tritiated substrate reacts a t only 200/0 the rate of the normal carrier species. Neither substrate nor product show significant proton exchange with the medium due to the enzyme.

No abstract

Ribulose-1 ,5-P, labelled with tritium in the C-3 position was converted to 2 moles of phosphoglyceric acid by the carboxydismutase. Over 98 Olio of the radioactivity was found in the water, less than 0.1 being in phosphoglyceric acid, indicating that the proton lost from the 3 position of the substrate does not contribute to the formation of product. The tritiated substrate reacts a t only 200/0 the rate of the normal carrier species. Neither substrate nor product show significant proton exchange with the medium due to the enzyme.Ribulose-1 ,5-P2 carboxydismutase catalyzes the reaction :H,COP c=o HCOH CO,H

On the irreversible conversion of glucose-6-phosphate to fructose-6-phosphate in H2O/HOT with glucose-6-phosphate-isomerase 8 - 10% of the tritium content per gram atom hydrogen in the water are incorporated. The corresponding figures for the enzymatical conversions of mannose-6-phosphate → fructose-6-phosphate, dihydroxyacetone phosphate → glyceraldehyde phosphate, phosphoenol pyruvate → pyruvate are 17 - 18, 15 and 16% respectively. When fructose-l,6-diphosphate is transferred into dihydroxyacetone phosphate 40-45% tritium is fixed and 40% when pyruvate is decarboxylated to acetaldehyde. The triose isomerase reaction is approximately 10% intramolecular.

Baker’s yeast was incubated anaerobically and aerobically in H2O/HOT with uniformly labeled 14C-glucose. After partial fermentation the tritium distribution in some intermediates was determined. The equilibriums glucose-6-phosphate ⇄ frucose 6-phosphate ⇄ mannose-6-phosphate has not been reached. The tritium distribution in mannose-6-phosphate markedly differs from that in glucose- and fructose-6-phosphate. In fructose-1,6-diphosphate C-3, 4 and 5 have obtained the highest tritium label possible. The tritium content in the methyl group of ethanol is in good agreement with that obtained by adding up the tritium incorporation of every single step determined experimentally.