Concerted Action of Lactate Oxidase and Pyruvate Oxidase in Aerobic Growth of Streptococcus pneumoniae: Role of Lactate as an Energy Source
Concerted Action of Lactate Oxidase and Pyruvate Oxidase in Aerobic Growth of Streptococcus pneumoniae: Role of Lactate as an Energy Source
复制标题
乳酸氧化酶和丙酮酸氧化酶在肺炎链球菌有氧生长中的协同作用：乳酸作为能量来源的作用
作者：
Hiroaki Taniai;Ken‐ichiro Iida;Masanori Seki;M. Saito;S. Shiota;H. Nakayama;S. Yoshida
摘要肺炎链球菌除了具有丙酮酸氧化酶外，还具有乳酸氧化酶。这两个H2 O2形成氧化酶在野生型文化的活动是可检测的，即使在早期的指数增长期，并达到最高水平，在早期的稳定期。对于这些氧化酶中的每一种，构建缺陷突变体，并与亲本在需氧培养物中丙酮酸和乳酸的动力学进行比较。所获得的结果表明，野生型中的产能代谢可以通过以下方案最好地描述。(i)只要葡萄糖是可用的，通过丙酮酸氧化酶和乙酸激酶的顺序作用将形成的丙酮酸的大约四分之一转化为乙酸，并获得额外的ATP;（ii）其余的丙酮酸被乳酸脱氢酶还原形成乳酸，部分实现氧化还原平衡;（iii）乳酸盐被乳酸氧化酶氧化回丙酮酸盐，丙酮酸盐如上所述转化成乙酸盐;和（iv）只要存在乳酸盐，上述顺序反应就继续发生。正如该模型所预测的，外源添加的乳酸盐显示出在两种氧化酶存在下增加最终的生长产率。
ABSTRACT Streptococcus pneumoniae was shown to possess lactate oxidase in addition to well-documented pyruvate oxidase. The activities of both H2O2-forming oxidases in wild-type cultures were detectable even in the early exponential phase of growth and attained the highest levels in the early stationary phase. For each of these oxidases, a defective mutant was constructed and compared to the parent regarding the dynamics of pyruvate and lactate in aerobic cultures. The results obtained indicated that the energy-yielding metabolism in the wild type could be best described by the following scheme. (i) As long as glucose is available, approximately one-fourth of the pyruvate formed is converted to acetate by the sequential action of pyruvate oxidase and acetate kinase with acquisition of additional ATP; (ii) the rest of the pyruvate is reduced by lactate dehydrogenase to form lactate, with partial achievement of redox balance; (iii) the lactate is oxidized by lactate oxidase back to pyruvate, which is converted to acetate as described above; and (iv) the sequential reactions mentioned above continue to occur as long as lactate is present. As predicted by this model, exogenously added lactate was shown to increase the final growth yield in the presence of both oxidases.