CHANGES IN LEVELS OF ENZYMES OF PHENYLPROPANOID AND FLAVONOID SYNTHESIS DURING PHASEOLLIN PRODUCTION IN CELL-SUSPENSION CULTURES OF PHASEOLUS-VULGARIS

The extractable activities of phenylalanine ammonia-lyase, cinnamic acid 4-hydroxylase, p-coumaric acid-coenzyme A ligase, flavanone synthase and chalcone-flavanone isomerase showed significant increases in bean cell cultures in response to treatment with autoclaved ribonuclease, a potent inducer of phaseollin biosynthesis in this system. Increases in the activities of all the enzymes occurred within 6 h after ribonuclease treatment, but the subsequent development of activities was not coordinated. The flavanone synthase catalysed the formation of naringenin (4′,5,7-trihydroxyflavanone) from malonyl coenzyme A and p-coumaroyl coenzyme A. Synthesis of liquiritigenin (4′,7-dihydroxyflavanone) was not detected when soluble cytoplasmic or particulate preparations were incubated with the above substrates in the presence of NADPH or NADH generating systems. The results are discussed in terms of current views on isoflavonoid biosynthesis and the known changes in phenylpropanoid metabolism occurring in the cultures. © 1978.