亮氨酸对大鼠肝、肾色氨酸-烟酰胺代谢途径中酶的影响。
Effect of leucine on enzymes of the tryptophan-niacin metabolic pathway in rat liver and kidney.
机构信息
National Institute of Nutrition, Indian Council of Medical Research, Hyderabad-500007, India.
出版信息
Biochem J. 1973 Jun;134(2):425-30. doi: 10.1042/bj1340425.
Dietary excess of leucine affects tryptophan-niacin metabolism adversely and has thus been implicated in the etiology of pellagra. To understand the biochemical basis of leucine-induced changes in tryptophan-niacin metabolism the effect of leucine on enzymes of tryptophan-niacin metabolism was investigated. Excess of leucine in the diet had no effect on rat liver 3-hydroxyanthranilate oxygenase and nicotinate phosphoribosyltransferase but significantly decreased the activity of quinolinate phosphoribosyltransferase of rat liver and kidney. The activities of tryptophan oxygenase in liver and picolinate carboxylase in kidney were significantly higher in leucine-fed animals than in the controls. Also, oxidation of [U-(14)C]tryptophan in vivo was higher in leucine-fed animals. Increased picolinate carboxylase and decreased quinolinate phosphoribosyltransferase activities would result in a decrease in NAD formation from dietary tryptophan. Lowered NAD formation from tryptophan particularly when the niacin concentrations in the diet are marginal would result in a state of conditioned niacin deficiency.
膳食中亮氨酸过量会对色氨酸-烟酰胺代谢产生不利影响，因此与糙皮病的病因有关。为了了解亮氨酸诱导的色氨酸-烟酰胺代谢变化的生化基础，研究了亮氨酸对色氨酸-烟酰胺代谢酶的影响。饮食中亮氨酸过量对大鼠肝脏 3-羟基犬尿氨酸加氧酶和烟酰胺磷酸核糖基转移酶没有影响，但显著降低了大鼠肝脏和肾脏喹啉酸磷酸核糖基转移酶的活性。亮氨酸喂养的动物肝脏中的色氨酸加氧酶和肾脏中的吡啶羧酸羧化酶的活性明显高于对照组。此外，亮氨酸喂养的动物体内 [U-(14)C]色氨酸的氧化也更高。吡啶羧酸羧化酶增加和喹啉酸磷酸核糖基转移酶减少会导致从膳食色氨酸形成 NAD 的减少。从色氨酸形成的 NAD 减少，特别是当饮食中烟酰胺浓度处于边缘状态时，会导致条件性烟酰胺缺乏状态。
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