Influence of amino acids upon insulin release evoked by 3-phenylpyruvate

Insulin release induced by 3-phenylpyruvate in rat pancreatic islets was unaffected by L-norleucine, L-valine, L-alanine and L-asparagine, but potentiated by L-glutamine, glycine and L-serine. The latter two amino acids also enhanced insulin secretion evoked by the combination of 3-phenylpyruvate and L-glutamine. Since 3-phenylpyruvate is known to stimulate insulin release by acting as a transamination partner and facilitating the catabolism of endogenous amino acids, the present findings suggest that the secretory efficiency of such a biochemical sequence depends upon the subcellular location of the transamination reaction and upon the interference of 3-phenylpyruvate with the transport of 2-keto acids into mitochondria.