DEFICIENT METABOLIC UTILIZATION OF HYDROGEN-PEROXIDE IN TRYPANOSOMA-CRUZI
DEFICIENT METABOLIC UTILIZATION OF HYDROGEN-PEROXIDE IN TRYPANOSOMA-CRUZI
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DOI：
10.1042/bj1880643
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发表时间：
1980-01-01
影响因子：
4.1
通讯作者：
STOPPANI, OM
中科院分区：
文献类型：
--
作者：
BOVERIS, A;SIES, H;STOPPANI, OM
研究了谷胱甘肽过氧化物酶-谷胱甘肽还原酶系统--过氧化氢代谢利用的替代途径--在缺乏过氧化氢酶和过氧化物酶缺陷型生物中的作用。谷胱甘肽的存在(4.9.+-.0.7nmoL还原型谷胱甘肽/108细胞)和NADPH依赖的谷胱甘肽还原酶(5.3+-.(0.4单位/108个细胞)，但以H_2O_2为底物的提取物不具有谷胱甘肽过氧化物酶活性。以叔丁基氢过氧化氢或异丙苯过氧化氢为底物，检测到非常低的NADPH依赖的谷胱甘肽过氧化物酶活性(相当于0.3-0.5单位的过氧化物酶/108细胞，或约10%的谷胱甘肽还原酶活性)。谷胱甘肽过氧化物酶测定的空白反应(过氧化氢对谷胱甘肽的非酶氧化和NADPH的酶氧化)阻碍了过氧化物酶活性的准确测量。上鞭毛提取液中存在超氧化物歧化酶和抗坏血酸过氧化物酶活性，而不存在过氧化氢酶。抗坏血酸过氧化物酶活性对氰化物敏感，对热不稳定，而以二氨基联胺、邻苯三酚或愈创木酚为电子供体则不显示活性。克氏毛滴虫上胚体可能缺乏足够的酶来防御过氧化氢和过氧化氢相关的自由基。
The glutathione peroxidase-glutathione reductase system, an alternative pathway for metabolic utilization of H2O2 was investigated in T. cruzi, an organism lacking catalase and deficient in peroxidase. The presence of glutathione (4.9 .+-. 0.7 nmol of reduced glutathione/108 cells) and NADPH-dependent glutathione reductase (5.3 .+-. 0.4 munit/108 cells) was demonstrated in the cytosolic fraction of the parasite, but with H2O2 as substrate glutathione peroxidase activity could not be demonstrated in the same extracts. With t-butyl hydroperoxide or cumene hydroperoxide as substrate, a very low NADPH-dependent glutathione peroxidase activity was detected (equivalent to 0.3-0.5 munit of peroxidase/108 cells, or about 10% of glutathione reductase activity). Blank reactions of the glutathione peroxidase assay (non-enzymic oxidation of glutathione by hydroperoxides and enzymic oxidation of NADPH) hampered accurate measurement of peroxidase activity. The presence of superoxide dismutase and ascorbate peroxidase activity in, and the absence of catalase from, epimastigote extracts was confirmed. Ascorbate peroxidase activity was cyanide-sensitive and heat-labile, but no activity could be demonstrated with diaminobenzidine, pyrogallol or guaiacol as electron donor. T. cruzi epimastigotes probably lack an adequate enzyme defense against H2O2 and H2O2-related free radicals.