Alston T A, Abeles R H
Graduate Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02254.
Arch Biochem Biophys. 1988 Feb 1;260(2):601-8. doi: 10.1016/0003-9861(88)90487-0.
Nicotinamide methyltransferase (EC 2.1.1.1) has been purified over 1300-fold from porcine liver. The enzyme is electrophoretically homogeneous, exhibiting a relative molecular mass of 27,000. In addition to acting on nicotinamide and close structural analogs such as thionicotinamide and 3-acetylpyridine, the enzyme actively accommodates poor analogs such as quinoline, isoquinoline, and 1,2,3,4-tetrahydroisoquinoline as methyl group acceptors. The enzyme may thus have the function of detoxicating numerous alkaloids in vivo. In some cases, the action of the enzyme might paradoxically increase the toxicities of substrates, but the hepatotoxic antibiotic pyrazinamide, which we considered as potentially such an enzyme-activated electrophile, did not function detectably as a substrate for the isolated enzyme.
烟酰胺甲基转移酶（EC 2.1.1.1）已从猪肝中纯化出来，纯化倍数超过1300倍。该酶在电泳上是均一的，相对分子质量为27,000。除作用于烟酰胺以及硫代烟酰胺和3-乙酰吡啶等结构类似物外，该酶还能有效地接纳喹啉、异喹啉和1,2,3,4-四氢异喹啉等较差的类似物作为甲基受体。因此，该酶可能具有在体内使多种生物碱解毒的功能。在某些情况下，该酶的作用可能反常地增加底物的毒性，但我们认为可能是这种酶激活的亲电试剂的肝毒性抗生素吡嗪酰胺，作为分离酶的底物时未检测到有作用。
