Diphosphatedependent

Diphosphate-dependent describes enzymes and reactions that rely on diphosphate cofactors, usually pyrophosphate (PPi), rather than ATP, to drive catalysis. In these systems PPi can act as a phosphoryl donor or be hydrolyzed to provide energy, enabling reactions that might be less favorable with ATP alone. PPi hydrolysis by pyrophosphatase helps pull reactions forward, contributing to energetic efficiency in some pathways.

Examples are common in bacteria, archaea, and plant plastids. Pyrophosphate-dependent phosphofructokinase (PPi-PFK) uses PPi to convert fructose-6-phosphate and PPi into fructose-1,6-bisphosphate and Pi, instead of ATP. PPi-dependent phosphoglycerate mutase (PPi-PGM) is involved in glycolytic or gluconeogenic steps in certain taxa. Pyruvate phosphate dikinase (PPDK) can couple PPi hydrolysis and phosphate transfer to interconvert pyruvate and phosphoenolpyruvate in some organisms.

Compared with ATP-dependent enzymes, diphosphate-dependent systems can save ATP equivalents and adapt to cellular energy budgets, though PPi must be efficiently managed to avoid energy loss. The term is commonly used in discussions of microbial metabolism and the evolution of energy-conserving strategies.

Note that diphosphate-dependent and PPi-dependent are often used interchangeably; the exact role of PPi varies among enzyme classes and organisms.