Reactivities of various amines in the modifications of acetic acid and aspartic acid-101 of lysozyme in the carbodiimide reaction.
作者:RYOTA KUROKI、NAOE KANESAKA、HIDENORI YAMADA、TAIJI IMOTO
DOI:10.1248/cpb.35.4203
日期:——
Reactivities of various amines in the modifications of acetic acid and Asp-101 of hen egg-white lysozyme in the carbodiimide (1-ethyl-3 [3- (dimethylamino) propyl]carbodiimide hydrochloride (EDC)) reaction were investigated at pH 5.0 and room temperature. The reactivity of an amine towards EDC-activated Asp-101 was at least 50 times higher than that towards EDC-activated acetic acid. Such a high efficiency of modification of Asp-101 could not be explained only by the EDC-binding mechanism in which the EDC molecule binds to the active site cleft of lysozyme close to Asp-101 to activate Asp-101 selectively [R. Kuroki, H. Yamada, and T. Imoto, J. Biochem. (Tokyo), 99, 1493 (1986)]. Therefore, in addition to the above mechanism, an amine-binding mechanism in which an amine molecule binds to lysozyme close to the EDC-activated Asp-101 residue so as to increase the effective concentration of the amine by more than 50 times is proposed.
在 pH 5.0 和室温条件下,研究了各种胺在碳化二亚胺(1-乙基-3 [3-(二甲基氨基)丙基]碳化二亚胺盐酸盐(EDC))反应中对醋酸和母鸡卵白溶菌酶 Asp-101 的修饰反应活性。胺对 EDC 活化的 Asp-101 的反应活性比对 EDC 活化的醋酸的反应活性至少高 50 倍。对 Asp-101 进行如此高效的修饰不能仅用 EDC 结合机制来解释,在该机制中,EDC 分子与靠近 Asp-101 的溶菌酶活性位点裂隙结合,从而选择性地激活 Asp-101[R. Kuroki, H. Yamada, and T. Imoto, J. Biochem. (Tokyo), 99, 1493 (1986)]。因此,除了上述机制外,还提出了一种胺结合机制,即胺分子与靠近 EDC 激活的 Asp-101 残基的溶菌酶结合,使胺的有效浓度增加 50 倍以上。