A Membrane Bound Cysteine Oxydase from the Cyanobacterium Synechococcus 6301

Abstract

Membrane fractions of the cyanobacterium Synechococcus 6301 obtained by french press treatment following sonication catalyzed an oxygen-dependent oxydation of cysteine to cystine. For 1 O2 consumed four cysteine were oxydized. Oxygen uptake was com pletely inhibited by 1 mM KCN. Only D- and L-cysteine were active and partial activity was observed with DL-homocysteine and cysteamine. No activity was found with glutathione, mercaptoethanol, thioglycerol, dithioerythritol, or N-acetyl-L-cysteine. Cysteines with a blocked acid group such O-methyl-L-cysteine and O-ethyl-L-cysteine were oxydized rapidly by Synechococcus membrane fractions. Rates of about 200 μmol of cysteine oxydized per mg chlorophyll and hour were measured. This cysteine respiration is discussed in relation to dark inactivation of enzymes. © 1983, Walter de Gruyter. All rights reserved.