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Oxygen sensitive pyruvate formate-lyase and its activating enzyme in oral microorganisms.

口腔微生物中氧敏感的丙酮酸甲酸裂解酶及其激活酶。

基本信息

批准号：
04671120
负责人：
ABE Kazuhiko
金额：
$ 1.34万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1994
项目状态：
已结题

项目摘要

Pyruvate formate-lyase (PFL) is a key enzyme of production of formic and acetic acid and ethanol by streptococci under anaerobic conditions. PFL was converted between oxygen-sensitive, active and oxygen tolerant, inactive forms in the cells of Streptococcus sanguis but not in the cells of Streptococcus mutans. All PFL was kept active in S.mutans cells. The biochmical mechanism of this difference in the interconversion was investigated. NADPH was the most efficient reducing agent for the activation of the inactive PFL of S.mutans. On the contrary, NADPH was not so efficient in S.sanguis. Fe^<2+> and selenium were required for PFL activating enzyme, and protein radial was involved in the active center of PFL.PFL inactivating enzyme, which converted active form to oxygen-tolerant inactive form, was found in streptococci. S.sanguis had higher activity of PFL inactivating enzyme than S.mutans.Intracellular conversion of PFL could be explained by these findings. Minute levels of pyruvate and inorganic phosphate inhibited the activity of PFL inactivating enzyme and kept active form of PFL.However, CoA enhanced PFL inactivation. These regulatory mechanism could be important teleologically. Glucose or sucrose metabolism was inhibited by sorbitol in S.mutans under certain conditions. The incorporation of sorbitol resulted in high NADH/NAD ratio and inhibited streptococcal sugar metabolism, since PFL activity was not enough to keep the oxidation/reduction balance. Sorbitol also inhibited sugar metabolism of microorganisms in dental plaque in situ.

丙酮酸甲酸裂解酶（PFL）是链球菌在厌氧条件下生产甲酸、乙酸和乙醇的关键酶。PFL在血链球菌细胞中可在氧敏感型、活性型和耐氧型、失活型之间转换，而在变形链球菌细胞中则不存在。所有PFL在s.a mutans细胞中保持活性。研究了这种相互转化差异的生化机制。NADPH是最有效的还原剂，以激活失活的s.a mutans PFL。相反，NADPH在血螺中没有那么有效。PFL激活酶需要Fe^<2+>和硒，蛋白质径向参与PFL的活性中心。在链球菌中发现PFL失活酶，将活性形式转化为耐氧失活形式。血螺的PFL灭活酶活性高于变形螺，可以解释PFL在细胞内的转化。微量的丙酮酸和无机磷酸盐抑制了PFL灭活酶的活性，保持了PFL的活性形态。然而，CoA增强了PFL的失活。这些调控机制在目的论上可能是重要的。山梨醇在一定条件下抑制变形链球菌的葡萄糖或蔗糖代谢。山梨醇的掺入导致NADH/NAD比例升高，抑制了链球菌的糖代谢，因为PFL活性不足以保持氧化/还原平衡。山梨醇还能抑制牙菌斑原位微生物的糖代谢。