REGULATION OF CARBOHYDRATE METABOLISM IN ORAL BACTERIA

这项调查试图描绘出涉及到的生化反应 一种细胞相关蛋白的失活和降解 唾液链球菌产生的果糖基转移酶(FTase)。我们 继续专注于FT失活步骤，因为该反应 似乎在休息时将酶标记为后续的蛋白质分解FT 细胞悬液与低浓度(0.5Fum)的 铜离子、FT呈时间依赖性失活。活动 该酶的无细胞制剂不受5.0Cu++H的影响。 细胞相关FT的失活需要分解代谢 内源性细胞内多糖或外源供应的葡萄糖和 被糖酵解抑制剂(碘乙酸酯、氟化钠和 Na2HAs04)。在饥饿的通透性细胞中，NADH可以取代葡萄糖 而NADPH或ATP则不能。在这些情况下FT的失活率 条件明显受到02的刺激，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。好氧培养的细胞具有高水平的NADH氧化酶和低水平的NADH氧化酶 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结果 在失活过程中牵涉到OH。Oh被认为是这样形成的： 1)FT-Cu+02通向FT-Cu++02)FT-Cu++H202通向FT-Cu++ +OH+OH减去H202和02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.