Effects of supersuppressor genes on enzymes controlling lysine biosynthesis in Saccharomyces.
Effects of supersuppressor genes on enzymes controlling lysine biosynthesis in Saccharomyces.
复制标题
超级抑制基因对控制酵母菌赖氨酸生物合成的酶的影响。
作者：
T. Fjellstedt;M. Ogur
研究了酵母超抑制基因对几种赖氨酸突变基因(ly(1-1)、ly(9-1)、ly(2-1))的作用及其对相应酶(糖苷脱氢酶、糖苷还原酶和α-氨基己二酸还原酶)的影响。在所有被测试的菌株中，超级抑制子通过允许未被抑制的突变体中没有的酶合成来发挥作用。分别从受抑制的ly(1-1)和ly(9-1)细胞中提取的糖胺脱氢酶和糖胺还原酶的光学方法研究表明，这两种酶的K(M)值显著大于野生型。被抑制的ly(9-1)细胞糖苷脱氢酶的K(M)值与野生型相似。这些发现与超级抑制子可能通过使无意义的密码子被读取而产生改变的酶蛋白的推断相一致。最近的研究发现，哺乳动物体内的赖氨酸降解可能与糖胺有关，人类的疾病，高赖氨酸血症和糖嘌呤尿症，可能是由于这种赖氨酸降解途径中的代谢障碍所致，这表明ly(1-1)和ly(9-1)酵母突变株可以作为人类状况及其可能的安非他命治疗的模型。
Yeast supersuppressor genes capable of masking the effects of several lysine mutant genes (ly(1-1), ly(9-1), ly(2-1)) were studied with respect to their effects on the respective enzymes (saccharopine dehydrogenase, saccharopine reductase, and alpha-amino-adipic acid reductase). In all strains tested, the supersuppressors functioned by allowing enzyme synthesis not found in the unsuppressed mutant. Studies by optical methods of saccharopine dehydrogenase and saccharopine reductase extracted from suppressed ly(1-1) and ly(9-1) cells, respectively, revealed that the K(m) values for these enzymes were significantly greater than those found in wild type. Saccharopine dehydrogenase from suppressed ly(9-1) cells was found to have K(m) values similar to wild type. These findings are consistent with the inference that a supersuppressor may act by enabling nonsense codons to be read, producing altered enzyme protein. Recent findings that lysine degradation in mammals may involve saccharopine and that the human diseases, hyperlysinemia and saccharopinuria, may be due to metabolic blocks in this route of lysine degradation suggest the ly(1-1) and ly(9-1) yeast mutants as models for the human condition and its possible euphenic treatment.