Portal de Periódicos da CAPES

Transamination of neutral amino acids and 2-keto acids in pancreatic B-cell mitochondria.

1985; Elsevier BV; Volume: 260; Issue: 23 Linguagem: Inglês

10.1016/s0021-9258(17)38917-2

1083-351X

Sigurd Lenzen, Wolfgang E. Schmidt, U. Panten,

Amino Acid Enzymes and Metabolism

High aminotransferase activities catalyzing the reactions between L-glutamate and L-glutamine and the aliphatic ketomonocarboxylic acids 2-ketoisocaproate, 2-ketocaproate, and 2-ketoisovalerate were observed in pancreatic B-cell mitochondria.While maximal rates of transamination with L-glutamate were observed .in the presence of micromolar Concentrations of keto acid, maximal rates of transamination with L- glutamine were recorded only in the presence of millimolar concentrations of keto acid.The insulin secretagogue 2-ketoisocaproate was the most effective transamination partner for L-glutamate, while the insulin secretagogue 2-ketocaproate was the most effective transamination partner for L-glutamine.Since B- cell mitochondria are well supplied with L-glutamate and L-glutamine, %ketoglutarate generation in the presence of these two neutral 2-keto acids may be an important prerequisite for their insulin secretory po- tency.High rates of transamination of 2-ketoglutarate were observed in the pancreatic B-cell mitochondria with the branched-chain amino acids L-leucine and L- valine, but not with L-norleucine.In connection with the ability of L-leucine to activate glutamate dehydrogenase, this high activity of the branched-chain amino acid aminotransferase in pancreatic.B-cell mitochondria may provide an explanation for the insulin secretory potency of this amino acid.