Department of Chemistry, Texas A&M University, College Station, 77843, United States.
J Am Chem Soc. 2012 Jun 6;134(22):9157-9. doi: 10.1021/ja302474a. Epub 2012 May 24.
In Saccharomyces cerevisiae , thiamin pyrimidine is formed from histidine and pyridoxal phosphate (PLP). The origin of all of the pyrimidine atoms has been previously determined using labeling studies and suggests that the pyrimidine is formed using remarkable chemistry that is without chemical or biochemical precedent. Here we report the overexpression of the closely related Candida albicans pyrimidine synthase (THI5p) and the reconstitution and preliminary characterization of the enzymatic activity. A structure of the C. albicans THI5p shows PLP bound at the active site via an imine with Lys62 and His66 in close proximity to the PLP. Our data suggest that His66 of the THI5 protein is the histidine source for pyrimidine formation and that the pyrimidine synthase is a single-turnover enzyme.
在酿酒酵母中，硫胺素嘧啶是由组氨酸和吡哆醛磷酸（PLP）形成的。先前已经使用标记研究确定了所有嘧啶原子的来源，这表明嘧啶的形成使用了非凡的化学物质，没有化学或生化先例。在这里，我们报告了密切相关的白色念珠菌嘧啶合酶（THI5p）的过表达，以及酶活性的重建和初步表征。白色念珠菌 THI5p 的结构显示 PLP 通过与赖氨酸 62 和组氨酸 66 紧密接近的亚胺结合在活性位点上。我们的数据表明，THI5 蛋白的组氨酸 66 是嘧啶形成的组氨酸来源，并且嘧啶合酶是一种单轮酶。
