Investigations

These investigations reveal that Synechocystis has neither an ED pathway nor a glucose dehydrogenase/glucokinase (GHD/GK) bypass. It rather contains a promiscuous aldolase EDA that prefers KDPG as substrate but also decarboxylates oxaloacetate (OAA) and cleaves 2-keto-4-hydroxyglutarate (KHG). In addition, the synthesis of KDPG from pyruvate and GAP is catalyzed with very low efficiency.

Cyanobacterial PFKs were thought to be ATP dependent, but isolation and characterisation of 2 PFK isoenzymes from Synechocystis revealed that they belong to the PFK-A family, use ADP as phosphate donor and form a separate phylogenetic class. Their allosteric regulation via 3-PG and ATP respectively allow for flexible switching between aactive and inactive enzymes dependent on the light and carbon status.