Modification of intracellular metabolism by expression of a C-terminal variant of phosphoribulokinase from Synechocystis sp. PCC 6803.

This article focuses on enhancing the activity of phosphoribulokinase (PRK), a key enzyme in the Calvin cycle of the cyanobacterium Synechocystis sp. PCC 6803, by introducing mutations in its C-terminal loop to prevent inhibitory disulfide bond formation. The study demonstrates that expressing a mutant PRK with cysteine-to-serine substitutions (Cys229Ser and Cys235Ser) increases intracellular PRK activity under photomixotrophic conditions without impairing growth. Metabolomic analysis revealed that this mutant strain accumulates higher levels of organic acids downstream of glycolysis and the tricarboxylic acid cycle, suggesting its potential for improved production of chemicals derived from these metabolites. These findings indicate that relieving oxidative suppression of PRK activity via targeted mutations offers a promising strategy for metabolic engineering in cyanobacteria.