BIOSYNTHESIS OF MUSTARD OIL GLUCOSIDES: V. FORMATION OF GLUCONASTURTIIN FROML-γ-PHENYLBUTYRINE-C14-N15IN WATERCRESS

Publisher Website
Google Scholar
Abstract
C14-labelled compounds were fed to watercress (Nasturtium officinale R. Br.) and their efficiency as precursors of the aglycone portion of gluconasturtiin compared. Phenylalanine-2-and -3-Cl4 and sodium ace-tate-2-C14 were efficient precursors of the aglycone but neither compound was as efficient a precursor as [gamma] -phenylbutyrine (2-amino-4-phenylbutyric acid). Approximately 40% of the C14 from [gamma] -phenyl-butyrine-2- or -3-C14 was incorporated into the aglycone side chain. Results of studies with doubly labelled L-[gamma] -phenylbutyrine-C14-N15 show that the amino nitrogen is incorporated directly into the thiogluco-side. Evidence that indicates that D- [gamma] -phenylbutyrine is converted to its L-isomer by the plant is also presented. The results of an isotope competition experiment provide some evidence for the existence of a chain-lengthening pathway (analogous to the formation of leucine from valine) for the biosynthesis of [gamma] -phenylbutyrine from phenylalanine and acetate in watercress.