Inhibition of transketolase by p-hydroxyphenylpyruvate

The effect of p-hydroxyphenylpyruvate, a natural analogue of transketolase substrate, on the catalytic activity of the enzyme was investigated. p-Hydroxyphenylpyruvate proved to be a reversible and competitive inhibitor of transketolase with respect to substrate; it was also able to displace thiamine diphosphate from holotransketolase. The data suggest that p-hydroxyphenylpyruvate participates in the regulation of tyrosine biosynthesis by influencing the catalytic activity of transketolase.