MEMBRANE ASSOCIATION OF SUCROSE SYNTHASE - CHANGES DURING THE GRAVIRESPONSE AND POSSIBLE CONTROL BY PROTEIN-PHOSPHORYLATION

Sucrose synthase (SuSy) plays an important role in sucrose degradation and occurs both as a soluble and as a membrane-associated enzyme in h igher plants, We show that membrane association can vary in vivo in re sponse to gravistimulation, apparently involving SuSy dephosphorylatio n, and is a reversible process in vitro. Phosphorylation of SuSy has l ittle effect on its activity but decreases its surface hydrophobicity as reported with the fluorescent probe bis-ANS. We postulate that phos phorylation of SuSy (and perhaps other membrane proteins) is involved in the release of the membrane-bound enzyme in part as a result of dec reased surface hydrophobicity. (C) 1997 Federation of European Biochem ical Societies.