Homogentisate 1,2-Dioxygenase (HGD) is an enzyme that is involved in carrying out one of the steps in the catalytic degradation of phenylalanine and tyrosine. Specifically, this step involves the oxidation of homogentisic acid, a catabolic derivative of both amino acids, to maleylacetoacetate. This latter compound is further acted on by other enzymes that break it down to other substrates, producing energy in the process.
