Babu B N, Brown O R
John M. Dalton Cardiovascular Research Center, Department of Veterinary Biomedical Sciences, University of Missouri, Columbia 65211, USA.
Microbios. 1995;82(332):157-70.
The [4Fe-4S] cluster-containing enzyme dihydroxy-acid dehydratase (DHAD) is susceptible to inactivation by dioxygen and active oxygen species including superoxide with an inactivation rate constant of 10(6) m-1 sec-1. Based on this property, DHAD was used to quantify and investigate the biological oxidant stress activity of various redox-cycling chemicals. Exponentially growing cultures of Escherichia coli were used as a sensitive source of the DHAD enzyme. The effects on DHAD of compounds with and without established redox activity, under aerobic and anaerobic (control) conditions were measured. Paraquat, juglone, nitrofurantoin, the nitrofuran related compound NF-963 which is 6,7-dihydro-3-(5-nitro-2-furyl-5H-imidazo-[2,1-b] thiazolium chloride), plumbagin, benzoquinone, duroquinone, hydralazine, and naphthalene inhibited DHAD activity and the concentrations required for 50% inhibition ranged from 3.5 microM for paraquat to 950 microM for naphthalene. Eleven other agents tested (including 4,4-dipyridyl which is a non-redox-cycling compound similar to paraquat and an extract and two compounds of plant origin) did not inhibit DHAD. The DHAD technique described is a useful means of detecting and comparing the oxidant-stress toxicity and mechanism of action of chemicals by a biological means on a quantitative scale relatable to paraquat.
含[4Fe-4S]簇的二羟基酸脱水酶（DHAD）易被氧气和包括超氧化物在内的活性氧物种灭活，其灭活速率常数为10(6) m-1秒-1。基于此特性，DHAD被用于定量研究各种氧化还原循环化学品的生物氧化应激活性。指数生长的大肠杆菌培养物被用作DHAD酶的敏感来源。测量了在需氧和厌氧（对照）条件下，具有和不具有既定氧化还原活性的化合物对DHAD的影响。百草枯、胡桃醌、呋喃妥因、6,7-二氢-3-(5-硝基-2-呋喃基-5H-咪唑-[2,1-b]噻唑鎓氯化物)的呋喃类相关化合物NF-963、白花丹素、苯醌、杜醌、肼苯哒嗪和萘抑制了DHAD活性，50%抑制所需的浓度范围从百草枯的3.5 microM到萘的950 microM。测试的其他11种试剂（包括与百草枯类似的非氧化还原循环化合物4,4-联吡啶以及一种提取物和两种植物来源的化合物）未抑制DHAD。所描述的DHAD技术是一种通过生物学手段在与百草枯相关的定量尺度上检测和比较化学品的氧化应激毒性及作用机制的有用方法。
