Catalyzes the conversion of 4-hydroxyphenylpyruvic acid to homogentisic acid, one of the steps in tyrosine catabolism (PubMed:10942115, PubMed:1339442, PubMed:34047349, PubMed:37794595). In addition may act as a N6-methyltransferase that methylates adenosine residues at the N(6) position of some RNAs (PubMed:10942115). {ECO:0000269|PubMed:10942115, ECO:0000269|PubMed:1339442, ECO:0000269|PubMed:34047349, ECO:0000269|PubMed:37794595}. This is the function of HPD (4-hydroxyphenylpyruvate dioxygenase, ENSG00000158104).