Nefedov L I, Bukhmet M I, Ostrovskiĭ Iu M, Moroz A R
Biokhimiia. 1989 Jul;54(7):1200-5.
A single intraperitoneal injection of nicotinamide (500 mg/kg) to mongrel albino rats causes a 6-hour increase in the 2-oxoglutarate level and the free NAD+/NADH ratio in liver mitochondria. The levels of taurine and taurocholates as well the activity of cysteine oxidase in liver tissues remains thereby unchanged, whereas the cysteine transaminase activity diminishes. In the heart and brain of experimental animals the activity of both enzymes is decreased. In the liver, blood plasma and heart of experimental animals, the Ala and Ser levels are low, whereas the taurine content is elevated both in blood plasma and brain. Nicotinamide administration eliminates positive correlations between the levels of taurine, its precursors and metabolically bound amino acids. In the liver the negative correlations between the activities of cysteine oxidase and cysteine transaminase observed in the control group disappear in the experimental group. Apparently, one of regulatory mechanisms of the taurine pool formation in the liver is the ratio of activities of the both enzymes as well as their competition at the substrate level. This emphasizes the importance of the transamination reactions in the metabolism of sulphur-containing amino acids.
给杂种白化大鼠腹腔内单次注射烟酰胺（500毫克/千克）会使肝脏线粒体中的2-氧代戊二酸水平和游离NAD⁺/NADH比值增加6小时。肝脏组织中牛磺酸和牛磺胆酸盐的水平以及半胱氨酸氧化酶的活性因此保持不变，而半胱氨酸转氨酶活性降低。在实验动物的心脏和大脑中，这两种酶的活性均降低。在实验动物的肝脏、血浆和心脏中，丙氨酸和丝氨酸水平较低，而血浆和大脑中的牛磺酸含量均升高。给予烟酰胺消除了牛磺酸、其前体和代谢结合氨基酸水平之间的正相关。在肝脏中，对照组中观察到的半胱氨酸氧化酶和半胱氨酸转氨酶活性之间的负相关在实验组中消失。显然，肝脏中牛磺酸池形成的调节机制之一是这两种酶的活性比例以及它们在底物水平上的竞争。这强调了转氨反应在含硫氨基酸代谢中的重要性。
