Biosynthesis of vitamin C during germination. IV. Effects of mitotoxic agents and certain enzyme inhibitors

Abstract

(1) Further studies on the changes in ascorbic acid elaboration by germinating müng with various cultural additions have been carried out with a view to elucidate the postulated role of intermediaries of glucose metabolism. (2) Selective inhibitors of certain enzymes concerned in glucose breakdown and in phosphorylation, such as azide, fluoride and 2:4 dinitrophenol adversely affect ascorbic acid formation. (3) Malonate, a competitive inhibitor of succinic dehydrogenase, depresses ascorbic acid elaboration. Involvement of fumarate in reactions leading to synthesis of ascorbic acid is thus inferable. (4) In proper concentrations, certain mitotoxic agents like chloretone, urethane and coumarin favour synthesis of ascorbic acid. (5) Phosphorylation inhibitors such as atabrine and 2:4 dinitrophenol adversely affect phosphatase and, more particularly, pyrophosphatase activities which are stimulated by fumarate or succinate and by mitotoxic agents like chloretone in suitable concentrations. Phosphorylation of intermediates seems therefore a necessary step in ascorbic acid elaboration. (6) In general, changes in nicotinic acid are parallel to those in ascorbic acid. (7) The related observations have been discussed and it is concluded that metabolic breakdown of glucose is a probable prerequisite to its transformation into ascorbic acid.