The Light-dependent Intermediary Metabolism of Phycomyces blakesleeanus BGFF. II. Formation and Degradation of Oxalacetic Acid

Abstract

Summary From light and dark-grown cultures of Phycomyces blakesleeanus BGFF. the concentrations of oxalacetate, malate, citrate, and of various amino acids were determined. The specific activities of different enzymes of the pathways forming or consuming oxalacetic acid were measured simultaneously. Significantly different values for light- and dark-grown cultures could be obtained either for some organic and amino acids or the specific activities of several enzymes. In illuminated cultures asparagine was present in a higher concentration, whereas alanine, malate, and citrate were accumulated more intensively in the dark. Parallel glutamate-pyruvate-transaminase and lactate dehydrogenase and the enzymes of the asparagine catabolism, asparaginase and glutamate-oxalacetate-transaminase, appeared more active in dark-grown cultures. The uptake of asparagine and glucose from the liquid nutrient was not effected by the light conditions. All data found indicate an increased asparagine catabolism in the dark via aspartate to oxalacetate that is metabolized more strongly and directly to citrate and malate and to alanine and lactate via phosphoenolpyruvate and pyruvate.