Sener A, Malaisse-Lagae F, Malaisse W J
J Biol Chem. 1983 Jun 10;258(11):6693-4.
In the absence of another exogenous nutrient, L-leucine but not L-norleucine stimulates insulin release from rat pancreatic islets, although the corresponding keto acids, 2-ketoisocaproate and 2-ketocaproate, are equally potent secretagogues. Such a situation cannot be ascribed to the preferential transamination of L-leucine as compared to L-norleucine in islet homogenates. Indeed, in the presence of a suitable activator of glutamate dehydrogenase, L-leucine and L-norleucine stimulate secretion to the same extent. It is concluded that the rate of transamination of these amino acids in intact islet cells depends on the availability of a 2-keto acid partner rather than on the assayed amino acid aminotransferase activity.
在缺乏其他外源性营养素的情况下，L-亮氨酸而非L-正亮氨酸能刺激大鼠胰岛释放胰岛素，尽管相应的酮酸，即2-酮异己酸和2-酮己酸，是同样有效的促分泌剂。这种情况不能归因于与胰岛匀浆中的L-正亮氨酸相比，L-亮氨酸的优先转氨作用。事实上，在谷氨酸脱氢酶的合适激活剂存在的情况下，L-亮氨酸和L-正亮氨酸刺激分泌的程度相同。得出的结论是，完整胰岛细胞中这些氨基酸的转氨速率取决于2-酮酸伴侣的可用性，而不是所检测的氨基酸转氨酶活性。
