Hydrogen peroxide production in Streptococcus pyogenes:: Involvement of lactate oxidase and coupling with aerobic utilization of lactate
Hydrogen peroxide production in Streptococcus pyogenes:: Involvement of lactate oxidase and coupling with aerobic utilization of lactate
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DOI：
10.1128/jb.186.7.2046-2051.2004
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发表时间：
2004-04-01
影响因子：
3.2
通讯作者：
Yoshida, S
中科院分区：
文献类型：
--
作者：
Seki, M;Iida, K;Yoshida, S
化脓性链球菌可分为两类，一类能产生过氧化氢，另一类不能产生过氧化氢(M.Saito，S.Ohga，M.Endoh，H.Nakayama，Y.Mizunoe，T.Hara，and S.Yoshida，Microbiology 147：2469-2477,2001)。在目前的研究中，这种二分法被证明平行于通透性细胞中产生过氧化氢的乳酸氧化酶活性的存在或不存在。在好氧条件下，只有在葡萄糖耗尽后才能检测到乳酸氧化酶活性和H_2O_2的产生。因此，可抑制葡萄糖的乳酸氧化酶可能是化脓性链球菌产生过氧化氢的原因。在该细菌的另外两种潜在的产生过氧化氢的酶，NADH和α-甘油磷酸氧化酶中，只有前者在这两类菌株中都表现出较低的但显著的活性。这种活性与生长阶段无关，提示该蛋白可能在体内作为H_2O_2清除酶NAD(P)H-连接的烷基氢过氧化氢还原酶的一个亚单位。乳酸氧化酶的活性与膜相关，而NADH氧化酶的活性位于可溶性部分，这与它们各自的生理作用，即产生和清除H_2O_2相一致。对发酵产物的分析表明，在培养过程中，乳酸的浓度随着时间的延长而增加，在葡萄糖耗竭时下降，而醋酸盐的浓度在培养过程中增加。这些结果表明，产生过氧化氢的细胞的乳酸氧化酶活性将乳酸氧化成丙酮酸，丙酮酸再转化为醋酸盐。后一个过程可能通过乙酰辅酶A和乙酰磷酸形成额外的ATP。
Streptococcus pyogenes strains can be divided into two classes, one capable and the other incapable of producing H2O2 (M. Saito, S. Ohga, M. Endoh, H. Nakayama, Y. Mizunoe, T. Hara, and S. Yoshida, Microbiology 147:2469-2477, 2001). In the present study, this dichotomy was shown to parallel the presence or absence of H2O2-producing lactate oxidase activity in permeabilized cells. Both lactate oxidase activity and H2O2 production under aerobic conditions were detectable only after glucose in the medium was exhausted. Thus, the glucose-repressible lactate oxidase is likely responsible for H2O2 production in S. pyogenes. Of the other two potential H2O2-producing enzymes of this bacterium, NADH and alpha-glycerophosphate oxidase, only the former exhibited low but significant activity in either class of strains. This activity was independent of the growth phase, suggesting that the protein may serve in vivo as a subunit of the H2O2-scavenging enzyme NAD(P)H-linked alkylhydroperoxide reductase. The activity of lactate oxidase was associated with the membrane while that of NADH oxidase was in the soluble fraction, findings consistent with their respective physiological roles, i.e., the production and scavenging of H2O2. Analyses of fermentation end products revealed that the concentration of lactate initially increased with time and decreased on glucose exhaustion, while that of acetate increased during the culture. These results suggest that the lactate oxidase activity of H2O2-producing cells oxidizes lactate to pyruvate, which is in turn converted to acetate. This latter process proceeds presumably via acetyl coenzyme A and acetyl phosphate with formation of extra ATP.