Metabolism of pyruvic acid-2-C14 and hydroxypyruvic acid-2-C14 in algae.

The metabolism of pyruvic acid in the light and dark by Scenedesmus has been examined with two aims: to study the relationship of its metabolism to that of the intermediates of C1402 fixation and to compare its metabolic fate with that of hydroxypyruvate. The metabolism of hydroxypyruvic acid was compared with that of C1402 fixation in order to ascertain whether it might be a photosynthetic intermediate or a substrate for the enzyme systems present. Since phosphohydroxypyruvate is a possible carboxylation product of ribulose diphosphate, the metabolism of the free acid was considered of interest. Stafford et al. (1) observed high n-glyceric acid dehydrogenase activity in a variety of leaves and suggested the possibility of its funct,ion in pentose phosphate carboxylation. The present work suggests rather that hydroxypyruvic acid may act largely as a substrate for transketolase or a hydroxypyruvic acid oxidase (2). Pyruvate-2-Cl4 and hydroxypyruvate-2-Cl4 were prepared on a small scale. The green alga, Scenedesmus, was allowed to photosynthesize in the presence of these substrates at low pH consistent with optimal assimilation of relatively strong organic acids. The products formed in the algae during light and dark periods were examined by two-dimensional paper chromatography.