Determination of the catalytic pathway of C4-leaf pyruvate, orthophosphate dikinase from maize.

The mechanism of the maize pyruvate, phosphate dikinase-catalyzed conversion of adenosine 5'-triphosphate, orthophosphate and pyruvate to adenosine 5'-monophosphate, inorganic pyrophosphate and phosphoenolpyruvate, respectively, was determined by using transient kinetic techniques. The data obtained demonstrate that catalysis in the maize pyruvate, phosphate dikinase active site involves initial transfer of the P beta P-unit from adenosine 5'-trisphosphate to the enzyme to form a pyrophosphorylenzyme intermediate, followed by sequential phosphoryl group transfer to orthophosphate (to form pyrophosphate and a phosphoenzyme intermediate) and pyruvate (to form phosphoenolpyruvate and free enzyme).