Kawamura Shunsuke, Toshima Gen, Chijiiwa Yuki, Torikata Takao, Araki Tomohiro
Department of Bioscience, School of Agriculture, Tokai University, Aso, Kumamoto, Japan.
Biosci Biotechnol Biochem. 2012;76(4):691-8. doi: 10.1271/bbb.110819. Epub 2012 Apr 7.
The amino acid sequence of Egyptian goose lysozyme (EGL) from egg-white and its enzymatic properties were analyzed. The established sequence had the highest similarity to wood duck lysozyme (WDL) with five amino acid substitutions, and had eighteen substitutions difference from hen egg-white lysozyme (HEL). Tyr34 and Gly37 were found at subsites E and F of the active site when compared with HEL. The experimental time-course characteristics of EGL against the N-acetylglucosamine pentamer substrate, (GlcNAc)(5), revealed higher production of (GlcNAc)(4) and lower production of (GlcNAc)(2) when compared with HEL. The saccharide-binding ability of subsites A-C in EGL was also found to be weaker than in HEL. An analysis of the enzymatic reactions of five mutants in respect of positions 34, 37 and 71 in HEL indicated the time-course characteristics of EGL to be caused by the combination of three substitutions (F34Y, N37G and G71R) between HEL and EGL. A computer simulation of the EGL-catalyzed reaction suggested that the time-course characteristics of EGL resulted from the difference in the binding free energy for subsites A, B, E and F and the rate constant of transglycosylation between EGL and HEL.
对埃及雁蛋清溶菌酶（EGL）的氨基酸序列及其酶学性质进行了分析。所确定的序列与林鸳鸯溶菌酶（WDL）相似度最高，有五个氨基酸替换，与鸡蛋清溶菌酶（HEL）有18个替换差异。与HEL相比，在活性位点的E和F亚位点发现了Tyr34和Gly37。EGL作用于N-乙酰葡糖胺五聚体底物（GlcNAc）5的实验时间进程特征显示，与HEL相比，（GlcNAc）4的生成量更高，（GlcNAc）2的生成量更低。还发现EGL中A-C亚位点的糖结合能力比HEL弱。对HEL中34、37和71位的五个突变体的酶促反应分析表明，EGL的时间进程特征是由HEL和EGL之间的三个替换（F34Y、N37G和G71R）组合引起的。EGL催化反应的计算机模拟表明，EGL的时间进程特征是由EGL和HEL之间A、B、E和F亚位点结合自由能的差异以及转糖基化速率常数的差异导致的。
