Braus G H, Luger K, Paravicini G, Schmidheini T, Kirschner K, Hütter R
Microbiological Institute, Swiss Federal Institute of Technology, Zurich, Switzerland.
J Biol Chem. 1988 Jun 5;263(16):7868-75.
Transcription of the gene for phosphoribosyl-anthranilate isomerase (TRP1) from the TRP1 promoter is initiated only approximately half as frequently as, for example, from the TRP3 promoter, but TRP1 mRNA is approximately twice as stable as TRP3 mRNA. Therefore, the steady state amount of TRP1 mRNA in yeast cells, grown without amino acid limitation, is similar to the steady-state amount of TRP3 mRNA. The protein concentration of both enzymes in yeast cells is about the same, but the basal specific enzyme activity in permeabilized cells of the TRP1 gene product N-(5'-phosphoribosyl-1)-anthranilate isomerase is about 2-3 times higher than that of any of the other TRP enzymes. According to the kinetic parameters of the purified isomerase protein, the enzyme is more active than, for example, the purified TRP3 enzyme indoleglycerol-phosphate synthase. It is suggested that the TRP1 gene of Saccharomyces cerevisiae might be the result of a rearrangement event, separating the N-(5'-phosphoribosyl-1)-anthranilate isomerase domain from the indoleglycerol-phosphate synthase domain and putting the catalytically more active isomerase domain behind a weak and nonregulated constitutive promoter.
来自TRP1启动子的磷酸核糖基邻氨基苯甲酸异构酶（TRP1）基因的转录起始频率仅约为例如来自TRP3启动子的一半，但TRP1 mRNA的稳定性约为TRP3 mRNA的两倍。因此，在无氨基酸限制条件下生长的酵母细胞中，TRP1 mRNA的稳态量与TRP3 mRNA的稳态量相似。酵母细胞中这两种酶的蛋白质浓度大致相同，但TRP1基因产物N-（5'-磷酸核糖基-1）-邻氨基苯甲酸异构酶在透化细胞中的基础比酶活性比其他任何TRP酶高约2 - 3倍。根据纯化的异构酶蛋白的动力学参数，该酶比例如纯化的TRP3酶吲哚甘油磷酸合酶更具活性。有人提出，酿酒酵母的TRP1基因可能是重排事件的结果，将N-（5'-磷酸核糖基-1）-邻氨基苯甲酸异构酶结构域与吲哚甘油磷酸合酶结构域分开，并将催化活性更高的异构酶结构域置于一个弱的且无调控的组成型启动子之后。
