Studies on a possible reaction intermediate of p-hydroxyphenylpyruvate dioxygenase.

A quinol has been proposed to be an intermediate of the $\text{p}$-hydroxyphenylpyruvate dioxygenase-catalyzed reaction. However, using a highly purified enzyme from bovine liver and chemically synthesized quinol, no significant formation of homogentisate, the product of the enzymic reaction, from the quinol was observed under any conditions tested. Furthermore, the quinol showed no appreciable inhibition on the enzymic activity. In light of these findings, the reaction mechanism of the enzyme is discussed.