DITHIOTHREITOL AND COBALT EFFECTS ON MEMBRANE-ASSOCIATED PEROXIDASES OXIDIZING FERULOYL-COA

Membrane preparations from cell-suspension cultures of maize produced C-14-polymeric material from [methoxy-C-14]feruloyl-CoA under conditio ns reported to be suitable for the assay of feruloyl-CoA: polysacchari de feruloyltransferase activity. The major C-14-polymer formed did not contain O-[C-14]feruloyl-arabinofuranosyl groups. Production of C-pol ymer was prevented by catalase, indicating a requirement for endogenou s H2O2, and was Co2+-dependent but only in the presence of dithiothrei tol (DTT). The membranes exhibited peroxidase activity with guaiacol a nd H2O2; this reaction was blocked by DTT. It is concluded that peroxi dases and H2O2, endogenous to the isolated membranes, caused oxidative polymerization of [C-14]feruloyl groups of feruloyl-CoA; DTT prevente d polymerization by acting as a competitive substrate for peroxidases, and Co2+ restored polymerization by forming an insoluble complex with the thiol.