Qin Zhen, Yan Qiaojuan, Ma Qingjun, Jiang Zhengqiang
College of Food Science and Nutritional Engineering, Beijing Advanced Innovation Center of Food Nutrition and Human Health, China Agricultural University, Beijing 100083, China.
College of Engineering, China Agricultural University, Beijing 100083, China.
Biochem Biophys Res Commun. 2015 Oct 23;466(3):431-7. doi: 10.1016/j.bbrc.2015.09.043. Epub 2015 Sep 11.
L-serine ammonia-lyase, as a member of the β-family of pyridoxal-5'-phosphate (PLP) dependent enzymes, catalyzes the conversion of L-serine (L-threonine) to pyruvate (α-ketobutyrate) and ammonia. The crystal structure of L-serine ammonia-lyase from Rhizomucor miehei (RmSDH) was solved at 1.76 Å resolution by X-ray diffraction method. The overall structure of RmSDH had the characteristic β-family PLP dependent enzyme fold. It consisted of two distinct domains, both of which show the typical open twisted α/β structure. A PLP cofactor was located in the crevice between the two domains, which was attached to Lys52 by a Schiff-base linkage. Unique residue substitutions (Gly78, Pro79, Ser146, Ser147 and Thr312) were discovered at the catalytic site of RmSDH by comparison of structures of RmSDH and other reported eukaryotic L-serine ammonia-lyases. Optimal pH and temperature of the purified RmSDH were 7.5 and 40 °C, respectively. It was stable in the pH range of 7.0-9.0 and at temperatures below 40 °C. This is the first crystal structure of a fungal L-serine ammonia-lyase. It will be useful to study the catalytic mechanism of β-elimination enzymes and will provide a basis for further enzyme engineering.
L-丝氨酸氨裂解酶作为依赖磷酸吡哆醛（PLP）的β家族酶成员之一，催化L-丝氨酸（L-苏氨酸）转化为丙酮酸（α-酮丁酸）和氨。通过X射线衍射法以1.76 Å的分辨率解析了米黑根毛霉（RmSDH）的L-丝氨酸氨裂解酶的晶体结构。RmSDH的整体结构具有典型的β家族依赖PLP的酶折叠。它由两个不同的结构域组成，两者均呈现典型的开放扭曲α/β结构。一个PLP辅因子位于两个结构域之间的裂隙中，通过席夫碱连接与Lys52相连。通过比较RmSDH和其他已报道的真核L-丝氨酸氨裂解酶的结构，在RmSDH的催化位点发现了独特的残基取代（Gly78、Pro79、Ser146、Ser147和Thr312）。纯化后的RmSDH的最适pH和温度分别为7.5和40℃。它在pH 7.0 - 9.0范围内以及40℃以下的温度下稳定。这是真菌L-丝氨酸氨裂解酶的首个晶体结构。它将有助于研究β-消除酶的催化机制，并为进一步的酶工程提供基础。
