REGULATION OF CARBOHYDRATE METABOLISM IN ORAL BACTERIA

这项研究旨在描述参与的生化反应， 细胞相关蛋白的失活和蛋白水解降解 唾液链球菌产生的果糖基转移酶（FTase）。 我们 继续专注于FT灭活步骤，因为该反应 似乎“标记”酶，以便在休息时进行后续的蛋白水解FT 将细胞悬浮液与低浓度（0.5 μ M）的 铜离子，FT以时间依赖性方式失活。 活动 5.0 Cu++H对酶的无细胞制备物的pH值无影响。 细胞相关FT的失活需要 内源性细胞内多糖或外源性供应的葡萄糖， 糖酵解抑制剂（碘乙酸，氟化钠， Na2HAsO4）。 在饥饿的透化细胞中，NADH可以替代葡萄糖， 而NADPH或ATP则不能。 这些条件下的FT失活率 条件下显著刺激的O2，而其他几种酶 （谷氨酸脱氢酶，磷酸果糖激酶，醛缩酶）完全 稳定 需氧生长的细胞具有高水平的NADH氧化酶和低水平的 FT水平，而在微需氧条件下生长的细胞表现出 相反的关系。 氧自由基清除剂研究的结果 在灭活中涉及OH。 OH被认为是如下形成的： 1)2）FT-Cu + + H2 O2导致FT-Cu++ +OH+OH减去H2 O2和O2似乎是NADH氧化酶系统的产物。

This investigation seeks to delineate the biochemical reactions involved in the inactivation and proteolytic degradation of a cell-associated fructosyltransferase (FTase) produced by Streptococcus salivarius. We continue to concentrate on the FT inactivation step because this reaction appears to 'mark' the enzyme for subsequent proteolysis FT when resting cell suspensions were incubated with low concentrations (0.5f MuM ) of copper ions, FT was inactivated in a time dependent manner. The activity of a cell-free preparation of the enzyme was unaffected by 5.0 cu++H. Inactivation of the cell-associated FT required the catabolism of endogenous intracellular polysaccharide or exogenously supplied glucose and was prevented by inhibitors of glycolysis (iodoacetate, NaF, and Na2HAs04). In starved permeablized cells, NADH could replace glucose whereas NADPH or ATP could not. The rate of FT inactivation under these conditions was markedly stimulated by 02 while several other enzymes (glutamate dehydrogenase, phosphofructokinase, aldolase) were completely stable. Aerobically grown cells had high levels of NADH oxidase and low levels of FT, while cells grown under microaerophilic conditions exhibited the reverse relationship. Results from oxygen radical scavenger studies implicated OH in the inactivation. OH is thought to be formed as follows: 1) FT-Cu++ + 02 leads to FT-Cu++ 02 2) FT-Cu+ + H202 leads to FT-Cu++ +OH+OH minus H202 and 02 appear to be products of the NADH oxidase system.