The stimulus-secretion coupling of amino acid-induced insulin release: metabolism of L-asparagine in pancreatic islets.

The metabolism of L-asparagine in pancreatic islets was investigated. The deamidation of L-asparagine and the conversion of aspartate to oxalacetate, by transamination, may occur in both the cytosol and mitochondria. Oxalacetate is then converted to pyruvate in part via phosphoenolpyruvate and in part via malate. The latter modality, by consuming NADH and generating NADPH, may lead to changes in the redox state of the cytosolic NADH/NAD+ and NADPH/NADP+ couples. Such changes may in turn account, in part at least, for the capacity of L-asparagine to augment insulin release induced by certain nutrient secretagogues.