Abstract
Hanzlik et al. (1) observed the glycogenic action of propylene glycol in rats, and Lindberg (2) has isolated its phosphorylated ester from sea urchin eggs. The latter worker has subsequently demonstrat’ed the presence of 1 ,%propanediol phosphate (PDP) in other t’issues (3). Rudney (4, 5) has suggested that PDP might be an intermediate in the conversion of acetone to “formate” and Cz fragment, while Sakami and Lafaye (6) have suggested that PDP is an intermediate in Ohe metabolism of acetone and a precursor of a 3-carbon compound of the glycolytic cycle. Reports from this laboratory have suggested an alternative pathway of 3-carbon compounds of the glycolytic cycle (7, 8). It appeared to us that PDP might be an intermediate in the alternative pathway suggested by experiments in which slices of heart ventricle anabolizing lactic acid were not inhibited by a concentrat’ion of fluoride sufficient to inhibit enolase. Further, it occurred to us, in view of the recent observations of Harting (9), t,hat PDP might react in the same enzyme systems that normally oxidize cY-glycerophosphate, provided the primary alcohol group is not essential for cr-glycerophosphate dehydrogenase activity. The work reported here demonstrates the oxidation of PDP by a-glycerophosphate dehydrogenase and the removal of the end-product of this oxidation by a further oxidation by addition of a heart muscle extract (10). It has been found that a crystalline preparation of n-glyceraldehyde-3phosphate dehydrogenase will replace the heart’ muscle extract. The data suggest a new series of reactions by which the carbon of PDP might be diverted into pyruvic acid of the glycolytic cycle.
Highlights
The unusual stability of the phosphate ester of m-propylene glycol is demonstrated in Fig. 1. nn-Propanediol phosphate withstood alkaline hydrolysis (0.5 N) at 100” for 9 hours without liberation of any of the organic phosphate, and acid hydrolysis (5.0 N) liberated less than half of the organic phosphate during the same period of heating
It was desirable to determine whether the L form of propanediol phosphate (PDP) would stimulate oxygen uptake of rat liver homogenates
Per cent hydrolysis of nn-propanediol phosphate plotted against time in hours
Summary
The unusual stability of the phosphate ester of m-propylene glycol is demonstrated in Fig. 1. nn-Propanediol phosphate withstood alkaline hydrolysis (0.5 N) at 100” for 9 hours without liberation of any of the organic phosphate, and acid hydrolysis (5.0 N) liberated less than half of the organic phosphate during the same period of heating. In a preliminary experiment in which t,he spectrophotometric procedure was used, it was found that both a-glycerophosphate and Dr.,-propanediol phosphate were oxidized by myogen is, in the presence of DPN, P-glycerophosphate was not oxidized. Oxidation product of PDP, and further it seemed probable that monohydroxyacetone phosphate (a proposed intermediate) would not oxidize without prior rearrangement by isomerase action. The addition of this crystalline enzyme preparation to an equilibrium mixture of PDP and its oxidation product resulted in a further oxidation (see Fig. 3) These data suggest the presence of isomerase in one or both of the crystalline enzyme preparations. When myogen A was added to a rea.ction mixture containing cu-glycerophosphate, rapid oxidation to dihydroxyacetone phosphate [18] took place and equilibrium was established
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