Reaction of pyridoxamine-5-P with pyrroloquinoline quinone (coenzyme PQQ).

PQQ catalyzes the oxidation of pyridoxamine (PM) and pyridoxamine-5-P (PMP) to pyridoxal and pyridoxal-5-P (PLP) at 37 degrees C in the absence of micelles and proteins. The time course of conversion of PMP into PLP was monitored by absorption spectroscopy; a rate of 10 nmol PLP/min was determined. The product of the reaction was identified by TLC, HPLC and its ability to restore the catalytic activity of apoaspartate aminotransferase. The conversion of PMP into PLP by free PQQ is more efficient than reactions catalyzed by the enzymes plasma amine oxidase and pyridoxamine-5-P oxidase at optimal pH values.