The aerobic utilization of pyruvate in plant tissues

Abstract

Pyruvate with 14C-labelling in the carbonyl and methyl groups was supplied to apple tissue and to root tips of barley. After incubation of the labelling was found in a series of carboxylic acids and in alanine, glutamic acid, aspartic acid and gamma-amino-butyric acid. Glutamine and asparagine were also labelled; but several other amino acids whose presence was demonstrated were without label after 4 h. Sugars and polysaccharides were also unlabelled. The CO2 given off invariably contained 14C, but the specific activity was much lower than that of the pyruvate supplied. It is concluded that the fed pyruvate only very partially replaced internal substrates and that is was oxidized in a tricarboxylic acid cycle. It gave rise to alanine by direct animation and to other amino acids after partial oxidation. No pyruvate was built back to sugars or other carbohydrates in either tissue.