OXYGENASE SIDE REACTIONS OF CARBANION FORMING ENZYMES

几个，但不是全部，涉及碳离子的酶反应 中间体有相关的耗氧副反应，而不是 似乎需要氧气激活。除了加氧酶 核酮糖二磷酸羧基酶的反应，这些反应只有 最近被发现并严格测定了产品和 这些反应的机制尚未完成。An的表达 加氧酶副反应显然不止是一种可及性 碳离子反应，中间产物为分子氧。关于…的决定 各种加氧酶反应的所有产物，机理的评价 这些反应，以及它们的活动水平的可变性 来自不同来源的酶将有助于理解这些 反应。 氧气中毒通常被认为与三胞胎无关。 氧本身，但需要将O2转换为其单线态， 超氧化物、过氧化氢、羟基自由基或形成其他 激进分子。乙酰乳酸合成酶的加氧酶副反应 (鼠伤寒沙门氏菌)和谷氨酸脱羧酶(大肠杆菌) 分别提供过氧乙酸酯和过氧化氢作为产品，而 果糖二磷酸缩醛酶(金黄色葡萄球菌)的 能与蛋白质反应的产物，羟基丙酮醛磷酸盐。 这些反应与急性或慢性毒性(老化- 哺乳动物体内氧的相关功能丧失)尚不清楚，尤其是 由于相关酶的潜在加氧酶活性尚未被 检查过了。为此，哺乳动物的谷氨酸脱羧酶将 检查加氧酶反应，类似于最近发现的 来自大肠杆菌的酶。 将使用酶和化学方法的组合来确定 由这些酶产生的过氧化氢和超氧化物。红外线- 将使用灵敏的化学发光计来检测单线态氧。有机食品 和加氧酶反应的无机产物；氧化产物 酶和辅因子将通过质谱学进行评估。损失 这些酶的酶活性将在存在和 没有氧气和底物；在有或没有 保护剂。与高压氧暴露相关的急性氧中毒 氧气被认为是谷氨酸失活的结果。 大脑中的脱羧酶。通过以下方式了解分子机制 哪种氧气使这种酶失活和/或抑制可能导致 预防或治疗急性氧气的治疗剂的发展 毒性。这些结果也可能与慢性影响相关。 氧气对神经功能(如衰老)的影响。同样，加氧酶 其他酶的活性可能有助于非神经性哺乳动物的衰老 纸巾。

Several, but not all, enzymic reactions that involve carbanionic intermediates have associated oxygen-consuming side reactions that do not appear to require oxygen activation. With the exception of the oxygenase reaction of ribulosebisphosphate carboxylase, these reactions have only recently been discovered and a rigorous determination of the products and mechanisms of these reactions has not been completed. Expression of an oxygenase side reaction clearly involves more than accessibility of a carbanionic reaction intermediate to molecular oxygen. A determination of all products of various oxygenase reactions, evaluation of the mechanism of these reactions, and the variability in levels of activity for the same enzyme from various sources will contribute to an understanding of these reactions. Oxygen toxicity is generally not thought to be associated with triplet oxygen per se, but requires conversion of O2 to its singlet state, superoxide, hydrogen peroxide, hydroxyl radical, or the formation of other radicals. The oxygenase side reactions of acetolactate synthase (Salmonella typhimurium) and glutamate decarboxylase (Escherichia coli) give peracetate and hydrogen peroxide as products, respectively, while that of fructosebisphosphate aldolase (Staphylococcus aureus) gives a product capable of reacting with proteins, hydroxypyruvaldehyde phosphate. The relevance of these reactions to the acute or chronic toxicity (aging- related loss of function) of oxygen in mammals is unclear, especially since the potential oxygenase activities of relevant enzymes have not been examined. To this end the mammalian glutamate decarbexylase will be examined for an oxygenase reaction similar to that recently discovered for the enzyme from the bacterium Escherichia coli. A combination of enzymic and chemical methods will be used to determine hydrogen peroxide and superoxide production by these enzymes. An infrared- sensitive chemiluminometer will be used to detect singlet oxygen. Organic and inorganic products of the oxygenase reactions; oxidative products of the enzymes and cofactors will be assessed by mass spectroscopy. Losses of enzymic activity by these enzymes will be assessed in the presence and absence of oxygen and substrate; in the presence and absence of protectants. Acute oxygen toxicity associated with exposure to hyperbaric oxygen is thought to be a consequence of inactivation of glutamate decarboxylase in the brain. A knowledge of the molecular mechanism by which oxygen inactivates and/or inhibits this enzyme could lead to the development of therapeutic agents to prevent or to treat acute oxygen toxicity. These results could also be relevant to chronic effects of oxygen on neural function (e.g. aging). Similarly, the oxygenase activities of other enzymes may contribute to aging in nonneural mammalian tissues.