Guranowski A, Pawelkiewicz J
Eur J Biochem. 1977 Nov 1;80(2):517-23. doi: 10.1111/j.1432-1033.1977.tb11907.x.
Adenosylhomocysteinase from yellow lupin seeds (Lupinus luteus) has been purified to homogeneity. Active enzyme, Mr = 110000, consists of two probably identical subunits with Mr = 55000 as judged by gel filtration and dodecyl sulphage/polyacrylamide gel electrophoresis in the presence of 2-mercaptoethanol. The isoelectric point of the enzyme was shown to be 4.9 +/- 0.1. It was demonstrated by disc and pore gradient electrophoresis that the most purified fraction formed multimers. The enzyme shows optimum activity at pH 8.5-9.0. Km values are 2.3 micrometer, 4.6 mM and 12 micrometer for adenosine, DL-homocysteine and S-adenosyl-L-homocysteine, respectively. The energy of activation for S-adenosylhomocysteine synthesis was estimated as 14.4 kcal/mol (60.2 kJ/mol) and temperature coefficient as 2.4. The equilibrium constant for the hydrolysis of S-adenosylhomocysteine amounts to 5 X 10(-7) M. Anti-sulfhydryl reagents such as p-hydroxymercuribenzoate and N-ethylmaleimide acted as irreversible inhibitors. The enzyme exhibits high specificity for homocysteine whereas some of the rare nucleosides tested could substitute for adenosine.
从黄羽扇豆种子（羽扇豆）中提取的腺苷同型半胱氨酸酶已被纯化至同质。活性酶的分子量为110000，由两个可能相同的亚基组成，亚基分子量为55000，这是通过凝胶过滤以及在2-巯基乙醇存在下的十二烷基磺酸钠/聚丙烯酰胺凝胶电泳判断得出的。该酶的等电点为4.9±0.1。通过圆盘电泳和孔径梯度电泳证明，纯化程度最高的级分形成了多聚体。该酶在pH 8.5 - 9.0时表现出最佳活性。腺苷、DL-同型半胱氨酸和S-腺苷-L-同型半胱氨酸的米氏常数分别为2.3微摩尔、4.6毫摩尔和12微摩尔。S-腺苷同型半胱氨酸合成的活化能估计为14.4千卡/摩尔（60.2千焦/摩尔），温度系数为2.4。S-腺苷同型半胱氨酸水解的平衡常数为5×10⁻⁷摩尔。对巯基试剂如对羟基汞苯甲酸和N-乙基马来酰亚胺作为不可逆抑制剂起作用。该酶对同型半胱氨酸具有高度特异性，而一些测试的稀有核苷可以替代腺苷。
