Department of Bioengineering, College of Life Science, Dalian Minzu University, Dalian, 116600, Liaoning, China; Key Laboratory of Biotechnology and Bioresources Utilization (Dalian Minzu University), Ministry of Education, China.
Department of Bioengineering, College of Life Science, Dalian Minzu University, Dalian, 116600, Liaoning, China; Key Laboratory of Biotechnology and Bioresources Utilization (Dalian Minzu University), Ministry of Education, China; School of Life Science and Biotechnology, Dalian University of Technology, No 2 Linggong Road, Dalian, 116024, Liaoning, China.
Biochem Biophys Res Commun. 2019 Nov 5;519(2):274-279. doi: 10.1016/j.bbrc.2019.08.166. Epub 2019 Sep 5.
Lipases are widely present in various plants, animals and microorganisms, constituting a large category of enzymes. They have the ability to catalyze the cleavage of ester bonds. The lipase CinB from Enterobacter asburiae (E. asburiae) is an acetyl esterase. The primary amino acid sequence suggests that the EaCinB protein belongs to the α/β-hydrolase (ABH) superfamily of the esterase/lipase superfamily. However, its molecular functions have not yet been determined. Here, we report the crystal structure of E. asburiae CinB at a 1.45 Å resolution. EaCinB contains a signal peptide, cap domain and catalytic domain. The active site of EaCinB contains the catalytic triad (Ser180-His307-Asp277) on the catalytic domain. The oxyanion hole is composed of Gly106 and Gly107 within the conserved sequence motif HGGG (amino acid residues 106-109). The substrate is accessible between the α1 and α2 helices or the α1 helix and catalytic domain. Narrow substrate pockets are formed by the α2 helix of the cap domain. Site-directed mutagenesis showed that EaCinB-W208H exhibits a higher catalytic ability than EaCinB-WT by approximately nine times. Our results provide insight into the molecular function of EaCinB.
脂肪酶广泛存在于各种植物、动物和微生物中，构成了一大类酶。它们具有催化酯键断裂的能力。从洋葱伯克霍尔德氏菌（Enterobacter asburiae，E. asburiae）中分离得到的脂肪酶 CinB 是一种乙酰酯酶。其一级氨基酸序列表明，EaCinB 蛋白属于酯酶/脂肪酶超家族中的 α/β-水解酶（ABH）超家族。然而，其分子功能尚未确定。在这里，我们报道了 1.45 Å分辨率的 E. asburiae CinB 的晶体结构。EaCinB 包含一个信号肽、帽结构域和催化结构域。EaCinB 的活性位点包含催化三联体（Ser180-His307-Asp277）在催化结构域上。氧阴离子空洞由保守序列基序 HGGG（氨基酸残基 106-109）中的 Gly106 和 Gly107 组成。底物可在 α1 和 α2 螺旋或 α1 螺旋和催化结构域之间进入。由帽结构域的 α2 螺旋形成狭窄的底物口袋。定点突变显示，EaCinB-W208H 的催化能力比 EaCinB-WT 约高九倍。我们的研究结果为研究 EaCinB 的分子功能提供了思路。
