Hydrolysis of soluble, linear, un-cross-linked peptidoglycans by endogenous bacterial N-acetylmuramoylhydrolases.
Hydrolysis of soluble, linear, un-cross-linked peptidoglycans by endogenous bacterial N-acetylmuramoylhydrolases.
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通过内源性细菌 N-乙酰胞壁酰水解酶水解可溶性、线性、非交联的肽聚糖。
DOI：
10.1128/jb.159.2.520-526.1984
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发表时间：
1984
影响因子：
3.2
通讯作者：
Shockman,GD
中科院分区：
文献类型：
--
作者：
Barrett,JF;Schramm,VL;Shockman,GD
可溶性的，线性的，未交联的肽聚糖，从两个自溶缺陷的突变体的屎链球菌ATCC 9790和从微球菌leuteus制备，被用作底物的N-乙酰胞壁酰水解酶（胞壁酶）的水解研究。研究了这些底物的水解动力学和分离自S.屎肠球菌ATCC 9790和来自两个自溶缺陷突变体Lyt-14和Aut-3的菌株进行转糖基化反应的能力与鸡蛋白色溶菌酶（EC 3.2.1.17）的作用进行了比较。这些底物被内源性链球菌胞壁酶水解，产生了结构（式;见正文）几乎为唯一产物的双胍-肽单体。据估计，从减少基团的增加，水解进行了延长的时间间隔的线性速率，消耗高达75%的基板，即使在基板浓度远低于Km值。三种链球菌酶的表观Km和相对Vmax值彼此或与鸡蛋白色溶菌酶的Km和相对Vmax值难以区分。这些结果表明，这些突变体的自溶缺陷表型不能归因于它们的溶菌酶的差异。与鸡蛋白色溶菌酶的作用相反，链球菌溶菌酶不能催化转糖基。在恒定速率下的延长的水解期与酶-底物复合物形成后发生的多个催化事件一致。
Soluble, linear, uncross-linked peptidoglycans, prepared from two autolysis-defective mutants of Streptococcus faecium ATCC 9790 and from Micrococcus leuteus, were used as substrates for studies of hydrolysis by an N-acetylmuramoylhydrolase (muramidase). The kinetics of hydrolysis of these substrates and the ability of the muramidases isolated from S. faecium ATCC 9790 and from two autolysis-defective mutants, Lyt-14 and Aut-3, to carry out transglycosylation reactions were compared with the action of hen egg white lysozyme (EC 3.2.1.17). Hydrolysis of these substrates by the endogenous streptococcal muramidases resulted in the production of disaccharide-peptide monomers with the structure (formula; see text) as nearly the sole product. As estimated from increases in reducing groups, hydrolysis proceeded at a linear rate for extended intervals, with consumption of up to 75% of the substrate, even at substrate concentrations well below the Km value. Apparent Km and relative Vmax values for the three streptococcal enzymes were indistinguishable from each other or from those for hen egg white lysozyme. These results indicate that the autolysis-defective phenotype of these mutants cannot be attributed to differences in their muramidases. In contrast to the action of hen egg white lysozyme, the streptococcal muramidase failed to catalyze transglycosylations. The extended periods of hydrolysis at constant rates are consistent with the occurrence of multiple catalytic events after the formation of the enzyme-substrate complex.