Redox modifications of spinach chloroplast fructose-1,6-biophosphatase

Abstract

Complete activation of chloroplast fructose-1,6-bisphosphatase by dithiothreitol involves the reduction of its four disulfide bonds as revealed by thiol titration and activity measurement. Both before and after reduction, the enzyme is inhibited by the thiol-specific reagent 5,5'-dithiobis(2-nitrobenzoic acid) with complete inactivation upon modifications of the four accessible thiols. However, oxidative modification of the enzyme facillitates the reduction of the four mentioned disulfide bonds as the process of activation by DTT is accelerated.