Department of Microbiology and Immunology, Faculty of Pharmacy, Nahda University, Beni-Suef 62513, Egypt.
Biotechnology, Department of Chemistry, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
Biomolecules. 2019 Dec 27;10(1):45. doi: 10.3390/biom10010045.
Mycobacteriophage endolysins have emerged as a potential alternative to the current antimycobacterial agents. This study focuses on mycolylarabinogalactan hydrolase (LysB) enzymes of the α/β-hydrolase family, which disrupt the unique mycolic acid layer of mycobacterium cell wall. Multiple sequence alignment and structural analysis studies showed LysB-D29, the only enzyme with a solved three-dimensional structure, to share several common features with esterases (lacking lid domain) and lipases (acting on long chain lipids). Sequence and structural comparisons of 30 LysB homology models showed great variation in domain organizations and total protein length with major differences in the loop-5 motif harboring the catalytic histidine residue. Docking of different -nitrophenyl ligands (C4-C18) to LysB-3D models revealed that the differences in length and residues of loop-5 contributed towards wide diversity of active site conformations (long tunnels, deep and superficial funnels, shallow bowls, and a narrow buried cave) resembling that of lipases, cutinases, and esterases. A set of seven LysB enzymes were recombinantly produced; their activity against -nitrophenyl esters could be related to their active site conformation and acyl binding site. LysB-D29 (long tunnel) showed the highest activity with long chain -nitrophenyl palmitate followed by LysB-Omega (shallow bowl) and LysB-Saal (deep funnel).
分枝杆菌噬菌体内溶素已成为现有抗分枝杆菌药物的潜在替代品。本研究集中于α/β-水解酶家族的(mycolylarabinogalactan hydrolase) (LysB) 酶，该酶破坏分枝杆菌细胞壁独特的类脂酸层。序列比对和结构分析研究表明，唯一具有解决的三维结构的 LysB-D29 与酯酶（缺乏盖结构域）和脂肪酶（作用于长链脂质）共享几个共同特征。30 个 LysB 同源模型的序列和结构比较表明，结构域组织和总蛋白长度存在很大差异，主要区别在于含有催化组氨酸残基的环 5 基序。不同的 -硝基苯配体（C4-C18）与 LysB-3D 模型的对接表明，环 5 的长度和残基的差异导致活性部位构象的广泛多样性（长隧道、深和浅漏斗、浅碗和狭窄的埋藏洞穴）类似于脂肪酶、角质酶和酯酶。一组 7 种 LysB 酶被重组产生；它们对 -硝基苯酯的活性可以与其活性部位构象和酰基结合部位相关。LysB-D29（长隧道）对长链 -硝基苯棕榈酸显示出最高的活性，其次是 LysB-Omega（浅碗）和 LysB-Saal（深漏斗）。
