what is PEPA?and what is its role in biosynthetic phase?

PEPA stands for Phosphoenolpyruvic acid. It is formed from pyruvic acid by the enzyme pyruvate orthophosphate dikinase in mesophyll cells. It acts as the primary carbon dioxide acceptor in biosynthetic phase of C4 cycle and form first stable product, four carbon compound Oxaloacetic acid with the help of enzyme, PEPcase.