Einarsson J M, Sigmundsson K, Filippusson H
Department of Biochemistry, University of Iceland, Reykjavík, Iceland.
Comp Biochem Physiol B Biochem Mol Biol. 1996 May;114(1):41-8. doi: 10.1016/0305-0491(95)02116-7.
Carboxylesterase ESB3 was extracted from ovine liver and purified to homogeneity by ammonium sulphate fractionation, hydrophobic interaction chromatography on Phenyl Sepharose, ion exchange chromatography on Mono-Q Sepharose and size exclusion chromatography on Superose 6. The enzyme is free of carboxylesterase ESB2 activity. The molecular mass of the enzyme is estimated 182 kDa as judged by size exclusion chromatography. Isoelectric focusing indicates the presence of six isoforms of pI 5.50-5.77 with three main isoforms of pI 5.55-5.65. The enzyme is active towards the substrates p-nitrophenyl acetate and the aliphatic substrates ethyl acetate, ethyl propionate, ethyl butyrate, and ethyl valerate. Of the ethyl esters the affinity is lowest towards acetate and highest towards ethyl butyrate. The enzyme is totally inhibited by phenylmethylsulphonyl fluoride (PMSF) and mercuric chloride but not affected by eserine or cupric chloride. The pH optimum of the enzyme is 7.5 and it is stable at 55 degrees C for 20 min.
羧酸酯酶ESB3从绵羊肝脏中提取，通过硫酸铵分级分离、苯基琼脂糖疏水相互作用色谱、Mono-Q琼脂糖离子交换色谱和Superose 6尺寸排阻色谱纯化至同质。该酶无羧酸酯酶ESB2活性。通过尺寸排阻色谱判断，该酶的分子量估计为182 kDa。等电聚焦表明存在六种pI为5.50 - 5.77的同工型，其中三种主要同工型的pI为5.55 - 5.65。该酶对底物对硝基苯乙酸以及脂肪族底物乙酸乙酯、丙酸乙酯、丁酸乙酯和戊酸乙酯有活性。在乙酯类中，对乙酸乙酯的亲和力最低，对丁酸乙酯的亲和力最高。该酶被苯甲基磺酰氟（PMSF）和氯化汞完全抑制，但不受毒扁豆碱或氯化铜影响。该酶的最适pH为7.5，在55℃下稳定20分钟。
