Evidence of the Effect of opcA on the Catalytic Activity and Redox Sensitivity of Glucose-6-Phosphate Dehydrogenase of Synechocystis sp. PCC6803

Abstract

This study aimed at the analyses of G6PDH activity under presence of reducing agent DTTred using cell-free extracts of opcA− mutant Synechocystis sp. PCC6803 cells. K_m values of enzyme for both G6P and NADP was higher in cell-free extracts of the opcA− mutant in comparison with those of the wild type showing that the OpcA polypeptide plays a role to increase the substrate affinity of G6PDH. The enzyme was insensitive to DTT_red in opcA− mutant cell-free extract at pH 7.5 while the activity reduced about 29.31% in wild type cell-free extracts indicating that presence of the OpcA was necessary to alter redox state of the enzyme by DTT_red. Results of this study support that the OpcA protein, as one of the components of a cellular level regulation, plays an important role in redox modulation of cyanobacterial G6PDH.