Jakubowski H, Guranowski A
Biochemistry. 1981 Nov 24;20(24):6877-81. doi: 10.1021/bi00527a021.
Plant (Lupinus luteus) S-adenosylhomocysteinase, an alpha 2 dimer, forms a 1:2 enzyme-adenosine complex. The binding sites for adenosine are not equivalent. Binding of the first molecule of adenosine is fast (k greater than 7 x 10(5) M-1 s-1), whereas the second molecule of adenosine binds in a slow process with a half-life of 5 min. Adenosine in the 1:1 and 1:2 enzyme--substrate complexes reacts slowly (k = 0.05 min-1) to give finally free enzyme, adenine, and ribose. The enzyme does not lose its ability to catalyze the synthesis of S-adenosylhomocysteine during the reactions. The relevance of the data to the catalytic functioning of the plant S-adenosylhomocysteinase is discussed.
植物（羽扇豆）S-腺苷同型半胱氨酸酶是一种α2二聚体，可形成1:2的酶-腺苷复合物。腺苷的结合位点并不相同。第一个腺苷分子的结合速度很快（k大于7×10⁵ M⁻¹ s⁻¹），而第二个腺苷分子的结合过程较慢，半衰期为5分钟。1:1和1:2的酶-底物复合物中的腺苷反应缓慢（k = 0.05 min⁻¹），最终生成游离酶、腺嘌呤和核糖。在反应过程中，该酶不会丧失催化合成S-腺苷同型半胱氨酸的能力。文中讨论了这些数据与植物S-腺苷同型半胱氨酸酶催化功能的相关性。
