EXOENZYMATIC ACTIVITY OF TRANSGLYCOSYLASE ISOLATED FROM ESCHERICHIA-COLI
EXOENZYMATIC ACTIVITY OF TRANSGLYCOSYLASE ISOLATED FROM ESCHERICHIA-COLI
复制标题
DOI：
10.1111/j.1432-1033.1981.tb05342.x
复制
发表时间：
1981-01-01
期刊：
影响因子：
--
通讯作者：
SCHWARZ, U
中科院分区：
文献类型：
--
作者：
BEACHEY, EH;KECK, W;SCHWARZ, U
胞壁素转糖基酶（EC 3.2.1.-）大肠大肠杆菌可能作为一种外切酶，以系统的方式切割胞壁蛋白球囊进行了研究。这种水解酶的两个分子物种被分离和表征：一个是与可溶性部分，另一个是与包膜部分破裂的E。coli细胞。采用可溶性酶消化已用[3 H]二氨基庚二酸均匀标记的胞壁蛋白囊。对反应产物的分析表明，该酶不会随机切割聚糖链。为了确定转糖基酶是否首先从聚糖链的N-乙酰葡糖胺基或1，6-脱水胞壁酰末端释放胞肽，通过半乳糖基转移酶反应，在[14 C]-半乳糖的N-乙酰葡糖胺基末端进一步放射性标记[3 H]二氨基庚二酸标记的球囊。在消化过程早期，转糖基酶释放半乳糖标记的X + X“胞肽，表明聚糖链优先从N-乙酰葡糖胺基末端进行酶外切割。（X = N-乙酰葡糖胺基-1，6-脱水-N-乙酰胞壁酰-L-分析-D-γ-谷氨酰基-内消旋-二氨基庚二酸; X = X-D-丙氨酸。）的膜结合酶的活性的动力学是相同的可溶性酶，这表明这两种分子种类的转糖基酶的功能作为胞外酶在体外。
The possibility that murein transglycosylase (EC 3.2.1.-) of E. coli may function as an exoenzyme to cleave the murein sacculus in a systematic fashion was investigated. Two molecular species of this hydrolytic enzyme were isolated and characterized: one is associated with the soluble fraction and the other with the envelope fraction of ruptured E. coli cells. The soluble enzyme was employed to digest murein sacculi that had been uniformly labeled with [3H]diaminopimelic acid. The analysis of the reaction product indicated that the enzyme did not cleave the glycan chains randomly. To determine whether transglycosylase release muropeptide first from the N-acetylglucosaminyl or the 1,6-anhydromuramyl ends of the glycan chains, the [3H]diaminopimelate-labeled sacculi were further radiolabeled at their N-acetylglucosaminyl ends with [14C]- galactose by a galactosyl transferase reaction. The transglycosylase released galactose-labeled X + X'' muropeptides early during the course of digestion, suggesting exoenzymatic cleavage of the glycan chains preferentially from the N-acetylglucosaminyl ends. (X = N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-L-analyl-D-.gamma.-glutamyl-meso-diaminopimelic acid; X = X-D-alanine.) The kinetics of the activity of the membrane-bound enzyme were identical to that of the soluble enzyme, indicating that both molecular species of transglycosylase function as exoenzymes in vitro.