The Metabolism of Nicotinic Acid in the Green Pea and its Connection with Trigonelline

1. An active nicotinic acid metabolism has been established during the development of the green pea (fig. 3). 2. The nicotinic acid production, was inhibited by putting the plants in the dark or when the plants lack nitrogenous compounds. 3. We constructed an apparatus with which it was possible to determine in a simple way the amount of a substance absorbed by cut plants (fig. 4). 4. Cut pea plants were proved to have a normal nicotinic acid synthesis, therefore the leaves were supposed to synthesize nicotinic acid. 5. Above a definite level the nicotinic acid absorbed by the leaves is quantitatively transformed into trigonelline. 6. The balance-sheet of niacin was drawn up (table VI). From this we concluded that all pyridine compounds which take part in metabolism, are determined in our analyses, either as trigonelline or as nicotinic acid. 7. The nicotinic acid level of the pea retains a very constant value under normal physiological circumstances. 8. The addition of tryptophan, ornithine, citrulline, pyridoxine and pyruvic acid separately or in combination did not cause any increase of the nicotinic acid or trigonelline content. 9. The addition of tryptophan or ornithine with nitrogen free plants and of ornithine with plants in the dark gave the same results. 10. Therefore we concluded that the compounds mentioned above did not determine the rate of the nicotinic acid synthesis.