抄録
Distribution of nicotinate methyltransferase (EC 2.1.1.7) was investigated in nearly 100 kinds of samples of animals, plants and microorganisms. The enzyme activity was distributed widely in plants and the high activity was detected in leguminous plants. In animals, the enzyme activity was localized almost solely in marine fishes and shellfishes. The enzyme activity was not detected in land animals (including mammals and birds) and microorganisms. The highest 10 specific activities were in the order of tomato, chestnut, pea, field pea, marine clam, cherry, papaya melon, soybean young sprout, green soybean and corn (all are edible parts). A close relationship was observed between trigonelline content and the enzyme activity. Fundamental properties of the enzyme in the cell-free extracts of tomato, chestnut and marine clam were compared. The properties closely resembled each other. Namely, the optimum pH for the reaction was all 6.0, Km values for nicotinic acid were around 10 μM, and all were SH enzymes.
