Identification of the Anthocyanins in Petals of Tulip Varieties Smiling Queen and Pride of Haarlem.

resulted in increased indole disappearance. The omission of pyridoxal phosphate also markedly reduced the extent of indole disappearance. L-Serine rather than D-serine appeared to be involved in the coupling reaction. Glycine, threonine, homoserine, cysteine, alanine and glycolate were all unable to substitute for serine. pH dependence was studied in 3 different buffer systems. The overall results suggest low activity below pH 7, a sharp increase starting somewhere between 6.5 and 7, and a leveling-off somewhere near 8 or 8.5. Indole disappearance progressed at a constantly decreasing rate during the 100 minute incubation period studied. Expanded pea leaves also yielded active extracts. Preparations from stems, root tips, pods, and developing seeds, as well as plants other than the pea, did not promote serine-dependent indole disappearance. The results with pea cotyledons were uncertain. The tryptophan synthetase of pea buds appears to be very labile, and it is believed that the observed lack of activity in extracts of other plants may be partly attributable to enzyme lability. Chromatographic evidence suggests that in the pea bud system, the product of serine-dependent indole disappearance is tryptophan. It is concluded that pea bud extracts contain an enzyme analogous to tryptophan synthetase in microorganisms, and that tryptophan synthesis in the pea plant probably follows the same pathway as in microorganisms.