Nguyen-Distèche M, Leyh-Bouille M, Pirlot S, Frère J M, Ghuysen J M
Biochem J. 1986 Apr 1;235(1):167-76. doi: 10.1042/bj2350167.
In water, the purified 26 000-Mr membrane-bound DD-peptidase of Streptomyces K15 hydrolyses the ester carbonyl donor Ac2-L-Lys-D-Ala-D-lactate (release of D-lactate) and the amide carbonyl donor Ac2-L-Lys-D-Ala-D-Ala (release of D-alanine) with accumulation of acyl- (Ac2-L-Lys-D-alanyl-)enzyme. Whereas hydrolysis of the ester substrate proceeds to completion, hydrolysis of the amide substrate is negligible because of the capacity of the K15 DD-peptidase for utilizing the released D-alanine in a transfer reaction (Ac2-L-Lys-D-Ala-D-Ala + D-Ala----Ac2-L-Lys-D-Ala-D-Ala + D-Ala) that maintains the concentration of the amide substrate at a constant level. In the presence of an amino acceptor X-NH2 (Gly-Gly or Gly-L-Ala) related to the Streptomyces peptidoglycan, both amide and ester carbonyl donors are processed without detectable accumulation of acyl-enzyme. Under proper conditions, the acceptor activity of water and, in the case of the amide substrate, the acceptor activity of the released D-alanine can be totally overcome so that the two substrates are quantitatively converted into transpeptidated product Ac2-L-Lys-D-Ala-NH-X (and hydrolysis is prevented). Experimental evidence suggests that the amino acceptor modifies both the binding of the carbonyl donor to the enzyme and the ensuing rate of enzyme acylation.
在水中，链霉菌K15纯化的26000道尔顿膜结合DD-肽酶可水解酯羰基供体Ac2-L-赖氨酸-D-丙氨酸-D-乳酸（释放D-乳酸）和酰胺羰基供体Ac2-L-赖氨酸-D-丙氨酸-D-丙氨酸（释放D-丙氨酸），并积累酰基-（Ac2-L-赖氨酸-D-丙氨酰-）酶。酯底物的水解可进行到底，而酰胺底物的水解则可忽略不计，这是因为K15 DD-肽酶能够在转移反应（Ac2-L-赖氨酸-D-丙氨酸-D-丙氨酸+D-丙氨酸→Ac2-L-赖氨酸-D-丙氨酸-D-丙氨酸+D-丙氨酸）中利用释放的D-丙氨酸，从而使酰胺底物的浓度保持恒定。在存在与链霉菌肽聚糖相关的氨基受体X-NH2（甘氨酰-甘氨酸或甘氨酰-L-丙氨酸）的情况下，酰胺和酯羰基供体均可被处理，且不会检测到酰基酶的积累。在适当条件下，水的受体活性以及在酰胺底物情况下释放的D-丙氨酸的受体活性可被完全克服，从而使两种底物定量转化为转肽产物Ac2-L-赖氨酸-D-丙氨酸-NH-X（并防止水解）。实验证据表明，氨基受体既改变了羰基供体与酶的结合，也改变了随后的酶酰化速率。
