Mickelson M N, Anderson A J
Appl Environ Microbiol. 1984 Feb;47(2):338-42. doi: 10.1128/aem.47.2.338-342.1984.
Cystine reduction in Streptococcus agalactiae, resulting in sulfhydryl formation, may account for antagonism of the antibacterial effect of lactoperoxidase-thiocyanate-hydrogen peroxide when cystine is present in excess of the amount needed for maximum growth. Accumulation of cystine by S. agalactiae and its reduction to form sulfhydryl compounds were demonstrated. The reduction of cystine appeared to occur by a couple reaction between glutathione reductase and glutathione-disulfide transhydrogenase activity, both of which were found in the supernatant fraction from cell homogenates. NADPH-specific glutathione reductase activity was found in the pellet and supernatant fractions from cell homogenates. Two sulfhydryls were formed for each mole of NADPH used during cystine reduction. The information presented offers a plausible explanation of how cystine, when present in excess of growth needs, may be reduced to generate sulfhydryl compounds which neutralize the antibacterial effect of lactoperoxidase-thiocyanate-hydrogen peroxide on S. agalactiae.
无乳链球菌中胱氨酸的还原会导致巯基形成，当胱氨酸的量超过最大生长所需量时，这可能是导致乳过氧化物酶 - 硫氰酸盐 - 过氧化氢抗菌作用产生拮抗的原因。已证实无乳链球菌会积累胱氨酸并将其还原以形成巯基化合物。胱氨酸的还原似乎是通过谷胱甘肽还原酶和谷胱甘肽 - 二硫化物转氢酶活性之间的偶联反应发生的，这两种酶都存在于细胞匀浆的上清液部分。在细胞匀浆的沉淀和上清液部分都发现了NADPH特异性谷胱甘肽还原酶活性。在胱氨酸还原过程中，每使用一摩尔NADPH会形成两个巯基。所提供的信息为当胱氨酸的量超过生长需求时如何被还原以生成巯基化合物提供了一个合理的解释，这些巯基化合物会中和乳过氧化物酶 - 硫氰酸盐 - 过氧化氢对无乳链球菌的抗菌作用。
