Brown D M, Upcroft J A, Upcroft P
Queensland Institute of Medical Research, Bancroft Centre, Brisbane, Australia.
Mol Biochem Parasitol. 1995 Jun;72(1-2):47-56. doi: 10.1016/0166-6851(95)00065-9.
Non-denaturing polyacrylamide gels were used to analyse superoxide dismutase (SOD), catalase, peroxidase, NADH oxidase and NADH peroxidase in the microaerophilic protozoan parasite Giardia duodenalis. A cytosolic H2O-producing NADH oxidase and membrane-associated NADH peroxidase were readily detected from G. duodenalis. In all Giardia strains investigated the NADH oxidase was present in high levels (1.2-2 U (mg protein)-1). Using the same technique, NADH oxidase activity was also detected in the microaerophilic protozoan parasites Tritrichomonas foetus, Trichomonas vaginalis and Entamoeba histolytica and in the bacterium Escherichia coli. The conventional enzymes of oxidative stress management (superoxide dismutase, catalase and peroxidase) were not detected in particulate or cytosolic extracts from recent and established strains of Giardia assayed in situ. Spectrophotometric assays also yielded negative results. The same methodology readily detected one or more of these enzyme activities in T. foetus, T. vaginalis and E. coli. Superoxide dismutase activity was not detected in lines of Giardia resistant to high levels of metronidazole or furazolidone. Furthermore, the agents 1,10 phenanthroline, diamide, MnCl2 and KNO3, which induce SOD in anaerobically cultured E. coli, did not induce SOD in Giardia. 1,10 phenanthroline has also been shown to induce iron-containing (Fe-) SOD in Entamoeba. Neither peroxidase nor catalase activities were detected in a peroxide-resistant line of Giardia. Viable trophozoites from parent lines were able to decompose H2O2 at a significant rate. It appears that the conventional SOD, catalase and peroxidase utilised in aerobic metabolism have been substituted in Giardia by NADH oxidase and NADH peroxidase, similar to anaerobic bacteria. The O2-scavenging NADH oxidase explains the previously observed futile 'respiration' in Giardia.
使用非变性聚丙烯酰胺凝胶分析微需氧原生动物寄生虫十二指肠贾第虫中的超氧化物歧化酶（SOD）、过氧化氢酶、过氧化物酶、NADH氧化酶和NADH过氧化物酶。从十二指肠贾第虫中很容易检测到一种产生H2O的胞质NADH氧化酶和与膜相关的NADH过氧化物酶。在所研究的所有贾第虫菌株中，NADH氧化酶含量都很高（1.2 - 2 U（mg蛋白质）-1）。使用相同技术，在微需氧原生动物寄生虫胎儿三毛滴虫、阴道毛滴虫和溶组织内阿米巴以及大肠杆菌中也检测到了NADH氧化酶活性。在原位检测的近期和已建立的贾第虫菌株的颗粒或胞质提取物中，未检测到氧化应激管理的传统酶（超氧化物歧化酶、过氧化氢酶和过氧化物酶）。分光光度法检测也得出阴性结果。相同方法很容易在胎儿三毛滴虫、阴道毛滴虫和大肠杆菌中检测到这些酶活性中的一种或多种。在对高水平甲硝唑或呋喃唑酮耐药的贾第虫品系中未检测到超氧化物歧化酶活性。此外，在厌氧培养的大肠杆菌中诱导SOD的试剂1,10 - 菲咯啉、二酰胺、MnCl2和KNO3，在贾第虫中并未诱导出SOD。1,10 - 菲咯啉也已被证明可在溶组织内阿米巴中诱导含铁（Fe -）SOD。在对过氧化物耐药的贾第虫品系中未检测到过氧化物酶和过氧化氢酶活性。来自亲本品系的活滋养体能够以显著速率分解H2O2。看来，需氧代谢中使用的传统SOD、过氧化氢酶和过氧化物酶在贾第虫中已被NADH氧化酶和NADH过氧化物酶取代，类似于厌氧细菌。清除O2的NADH氧化酶解释了之前在贾第虫中观察到的无效“呼吸”现象。
