Distribution of Nicotinamide Methyltransferase and Fundamental Properties of the Enzyme in Hog Liver

Abstract

Distribution of nicotinamide methyltransferase (EC 2. 1. 1. 1) was investigated widely with 150 kinds of samples in animals, plants and microorganisms. The enzyme activity was found solely in animals and mostly in mammalian livers. Fundamental properties of nicotinamide methyltransferase in hog liver ex-tract were elucidated: optimum pH for the reaction, 5.0; Km values for nicotinamide and S-adenosyl-L-methionine, 58μM and 41μM, respectively; optimum temperature for the reaction (incubation period: 1 hr), 42℃; activation energy, 10,060cal/mol; inhibitors, heavy metal ions and N^1_methylnicotinamide (pro-duct inhibition, 50% at 30μM). The relationship among nicotinarnide methyltransferase, nicotinate methyltransferase (EC 2. 1. 1. 7) and nicotinamidase (EC 3. 5. 1. 19) in nature was discussed.