Purification and partial characterization of pyruvate decarboxylase from Oryza sativa L.

Pyruvate decarboxylase(PyrDC) was purified from rice bran to a specific activity of 1 mu kat/mg and partially characterized. The holoenzyme is a tetramer of two types of subunits with molecular masses 64 kDa and 62 kDa. Purified rice PyrDC exhibits positive cooperative kinetics with respect to pyruvate and functions with a significant lag phase. When compared to other plant PyrDC, the lag phase was shorter at low pyruvate concentrations and the S0.5 was smaller. The optimum pH (6.25) was also less acidic and the enzyme retained 30% of its maximal activity at neutral pH. In contrast to other plant PyrDC, rice PyrDC could be active at the onset of anoxia and would be activated by small changes in pyruvate concentration.