Nigam Ashwini Kumar, Kumari Usha, Mittal Swati, Mittal Ajay Kumar
Skin Physiology Laboratory, Centre of Advanced Study, Department of Zoology, Banaras Hindu University, Varanasi, 221 005, India.
Fish Physiol Biochem. 2014 Jun;40(3):635-44. doi: 10.1007/s10695-013-9872-9. Epub 2013 Oct 5.
Presence of carboxylesterase (CbE) activity in the skin mucus of Cirrhinus mrigala was investigated. CbE activity in skin mucus showed higher substrate preference for α-naphthyl acetate over p-nitrophenyl acetate. Four CbE isozymes-CbE-1, CbE-2, CbE-3, and CbE-4 were observed in skin mucus during zymography. The isozyme CbE-4 was characterized as typical serine esterase, whereas CbE-1, CbE-2, and CbE-3 were identified as sulphhydryl group-dependent serine esterases. In vitro treatment of skin mucus with the organophosphorus insecticide, Nuvan(®) showed strong inhibition of CbE activity. In vivo exposure of the fish to sublethal test concentrations (5 and 15 mg/l) of the insecticide also revealed significant inhibition of CbE activity in mucus. After the cessation of exposure, CbE activity recovered to its control level during the recovery periods. Thus, CbE activity in skin mucus could be considered a biomarker of the organophosphorus insecticide exposure to fish and a useful tool in monitoring environmental toxicity.
对印度鲮皮肤黏液中羧酸酯酶（CbE）活性的存在情况进行了研究。皮肤黏液中的CbE活性对α-萘乙酸的底物偏好高于对硝基苯乙酸。在酶谱分析过程中，在皮肤黏液中观察到了四种CbE同工酶——CbE-1、CbE-2、CbE-3和CbE-4。同工酶CbE-4被鉴定为典型的丝氨酸酯酶，而CbE-1、CbE-2和CbE-3被鉴定为依赖巯基的丝氨酸酯酶。用有机磷杀虫剂谷硫磷（®）对皮肤黏液进行体外处理显示对CbE活性有强烈抑制作用。将鱼体内暴露于该杀虫剂的亚致死试验浓度（5和15毫克/升）也显示黏液中的CbE活性受到显著抑制。在停止暴露后，CbE活性在恢复期恢复到对照水平。因此，皮肤黏液中的CbE活性可被视为鱼类接触有机磷杀虫剂的生物标志物以及监测环境毒性的有用工具。
