Seifert R, Hoshino J, Kröger H
Biochim Biophys Acta. 1984 Sep 28;801(2):259-64. doi: 10.1016/0304-4165(84)90075-8.
The distribution of cytosolic activity of nicotinamide:S-adenosylmethionine methyltransferase (nicotinamide methylase, EC 2.1.1.1) in normal tissues from adult rat and mouse and in tumors and the change in the enzyme activity during the development of rat tissues were studied. (1) Rat liver exhibited the highest nicotinamide methylase activity among all adult tissues tested; other rat tissues, like adrenal, pancreas, kidney, brain and mouse tissues, had only less than 15% of the adult rat liver activity. (2) 3 days before birth, fetal liver showed a very low nicotinamide methylase activity (2% of adult rat liver), which, however, increased already 1 day before birth and reached the adult level on the day 28 after birth. (3) In a variety of hepatomas and ascites tumors, an inverse correlation, with some exceptions, between tumor growth rate and nicotinamide methylase activity could be seen. In all hepatomas, with the exception of Morris hepatoma 5123tc, nicotinamide methylase activity was significantly decreased in comparison to normal adult rat liver. The highly malignant Zajdela hepatoma, Yoshida sarcoma, sarcoma 180 and Ehrlich ascites tumor methylated nicotinamide only at a negligibly low rate. (4) Cultured RLC cells (an established rat liver cell line) from the stationary growth phase or G1-arrested RLC cells had about half of the adult rat liver activity, yet the activity was 70% higher than that of the logarithmically growing RLC cells.
S-腺苷甲硫氨酸甲基转移酶（烟酰胺甲基酶，EC 2.1.1.1）在成年大鼠和小鼠正常组织以及肿瘤中的胞质活性分布，以及大鼠组织发育过程中该酶活性的变化。（1）在所有测试的成年组织中，大鼠肝脏的烟酰胺甲基酶活性最高；其他大鼠组织，如肾上腺、胰腺、肾脏、脑以及小鼠组织，其活性仅为成年大鼠肝脏活性的不到15%。（2）出生前3天，胎肝的烟酰胺甲基酶活性非常低（为成年大鼠肝脏的2%），然而，在出生前1天就已升高，并在出生后第28天达到成年水平。（3）在多种肝癌和腹水瘤中，除了一些例外情况，可以看到肿瘤生长速率与烟酰胺甲基酶活性呈负相关。在所有肝癌中，除了莫里斯肝癌5123tc外，与正常成年大鼠肝脏相比，烟酰胺甲基酶活性显著降低。高度恶性的扎伊德拉肝癌、吉田肉瘤、肉瘤180和艾氏腹水瘤对烟酰胺的甲基化速率极低。（4）处于静止生长期的培养RLC细胞（一种已建立的大鼠肝细胞系）或G1期停滞的RLC细胞的活性约为成年大鼠肝脏活性的一半，但该活性比对数生长期的RLC细胞高70%。
