Degradation of homovanillate by a strain ofVariovorax paradoxusvia ring hydroxylation

A newly isolated strain of Variovorax paradoxus could grow on homovanillate and several monohydroxylated phenylacetic acids. During growth on homovanillate, the organism formed separate NAD(P)H-dependent hydroxylases with activity towards 4-hydroxyphenylacetic acid and homovanillate. Homovanillate hydroxylase catalysed a typical monooxygenase reaction and had little activity towards 4-hydroxyphenylacetic acid GC-MS and TLC analysis suggested that homovanillate was 1-hydroxylated to yield a dihydroxymonomethoxyphenylacetic acid which served as a substrate for homogentisate 1,2-dioxygenase. Methanol, but not formaldehyde, was released either during ring-cleavage or subsequent metabolism of the ring-cleavage product.