The metabolism of exogenous hydroxyproline by gametophytes of Plagiochila arctica Bryhn et Kaal. (Hepaticae)

Abstract

The metabolic fate of free 4-hydroxyproline (Hyp), dual-labeled in specific positions, supplied to axenically cultured gametophytes of Plagiochila arctica was found to be complex. It could enter into at least three pathways, and the one that predominated depended on the concentration supplied. At low concentrations (i.e., 1 μM), free Hyp was mostly converted to proline (Pro) by a pathway in which pyrroline-5-carboxylate is the most probable intermediate. Lesser amounts entered a pathway(s) in which hydrogen was lost from the 3(2) carbon. And a small amount was directly incorporated into protein. At the higher concentrations that have been found to desuppress leaf and branch development in P. arctica the proportion of the labeled Hyp converted to Pro was markedly diminished and the proportion that was directly incorporated into peptide linkage was increased. This direct incorporation of Hyp into protein may be closely related to the ability of Hyp to relieve suppression of ventral leaves in leafy liverworts. the suppression-desuppression phenomenon is thought to involve cell surface and-or extracellular matrix proteins.