Goon D, Saxena M, Awasthi Y C, Ross D
Molecular Toxicology and Environmental Health Sciences Program, School of Pharmacy, University of Colorado Health Sciences Center, Denver 80262.
Toxicol Appl Pharmacol. 1993 Apr;119(2):175-80. doi: 10.1006/taap.1993.1058.
This study investigated the catalytic activities of hepatic glutathione S-transferase (GST) isoenzymes isolated from CD-1 mice toward two activated alkenals of toxicological relevance: trans,trans-muconaldehyde (MA), a putative myelotoxic metabolite of benzene, and trans-4-hydroxy-2-nonenal (HNE), a highly reactive lipid peroxidation product. The activity toward 1-chloro-2,4-dinitrobenzene (CDNB) was also determined. Four isoenzymes with pI values of 9.8, 8.7, 6.4, and 5.7 were each isolated from male and female mice. The isoenzymes with pI values of 8.7 and 6.4 are pi and mu class GSTs, respectively, whereas the pI 9.8 and 5.7 GSTs are both alpha class isoenzymes. CDNB activity was greatest in the pi (pI 8.7) isoenzyme of both sexes. In addition, the CDNB activity of the pi (pI 8.7) isoenzyme from males was markedly greater than the corresponding GST from female mouse liver. In contrast to CDNB, both MA and HNE were better substrates for the acidic alpha (pI 5.7) and mu (pI 6.4) GSTs, whereas minimal activity toward either alkenal was detected in the pi (pI 8.7) and alpha (pI 9.8) isoenzymes. Maximum activity toward MA and HNE was exhibited by the alpha (pI 5.7) isoenzyme of both sexes. The level of HNE activity observed with the alpha (pI 5.7) isoenzyme was five- to sixfold greater than that reported previously for any mouse GST isoenzyme. Moreover, the specific activities of the female alpha (pI 5.7) isoenzyme toward both HNE and MA were markedly greater than those of the corresponding isoenzyme from males. A similar gender-specific difference was noted in the activity of the mu (pI 6.4) isoenzyme toward HNE, but not toward MA. These results show that both MA and HNE are substrates for the alpha (pI 5.7) and mu (pI 6.4) GSTs of murine liver, with maximum activity toward both activated alkenals exhibited by the alpha (pI 5.7) isozyme. In addition, evidence is presented that demonstrates a female-dominant sex difference in the activity of the alpha (pI 5.7) isoenzyme toward MA and HNE, which contrasts sharply with the male-dominant activity of pi class GSTs toward CDNB. These results are consistent with the hypothesis that alpha and mu class GSTs are critical detoxication enzymes in female mouse liver, whereas pi-class GST isozymes predominate in the liver of male mice.
本研究调查了从CD-1小鼠中分离出的肝谷胱甘肽S-转移酶（GST）同工酶对两种具有毒理学相关性的活化烯醛的催化活性：反，反-粘糠醛（MA），一种推测的苯骨髓毒性代谢物，以及反式-4-羟基-2-壬烯醛（HNE），一种高反应性脂质过氧化产物。还测定了对1-氯-2,4-二硝基苯（CDNB）的活性。分别从雄性和雌性小鼠中分离出四种pI值为9.8、8.7、6.4和5.7的同工酶。pI值为8.7和6.4的同工酶分别是π和μ类GST，而pI 9.8和5.7的GST都是α类同工酶。CDNB活性在两性的π（pI 8.7）同工酶中最高。此外，雄性小鼠肝脏中π（pI 8.7）同工酶的CDNB活性明显高于雌性小鼠肝脏中的相应GST。与CDNB相反，MA和HNE都是酸性α（pI 5.7）和μ（pI 6.4）GST的更好底物，而在π（pI 8.7）和α（pI 9.8）同工酶中对任何一种烯醛的活性都检测到最低。两性的α（pI 5.7）同工酶对MA和HNE表现出最大活性。α（pI 5.7）同工酶观察到的HNE活性水平比先前报道的任何小鼠GST同工酶高五到六倍。此外，雌性α（pI 5.7）同工酶对HNE和MA的比活性明显高于雄性相应的同工酶。在μ（pI 6.4）同工酶对HNE的活性中也注意到类似的性别特异性差异，但对MA没有。这些结果表明，MA和HNE都是小鼠肝脏α（pI 5.7）和μ（pI 6.4）GST的底物，α（pI 5.7）同工酶对两种活化烯醛均表现出最大活性。此外，有证据表明，α（pI 5.7）同工酶对MA和HNE的活性存在女性主导的性别差异，这与π类GST对CDNB的男性主导活性形成鲜明对比。这些结果与以下假设一致，即α和μ类GST是雌性小鼠肝脏中的关键解毒酶，而π类GST同工酶在雄性小鼠肝脏中占主导地位。
