HUMAN 4-HYDROXPHENYLPYRUVATE DIOXYGENASE - PRIMARY STRUCTURE AND CHROMOSOMAL LOCALIZATION OF THE GENE

We report the primary structure of 4-hydroxyphenylpyruvate dioxygenase [4-hydroxyphenylpyruvate: oxygen oxidoreductase (hydroxylating, decar boxylating)]. The work is based on the isolation of cDNA clones from h uman liver lambdagt11 libraries. Several overlapping clones covering t he coding sequence were characterized. In parallel, peptides from four different digests of the purified protein were analysed for their ami no-acid sequence. These peptide sequences covered 86% of the cDNA-deri ved amino-acid sequence. This gives the sequence for a polypeptide of 392 amino acids with a calculated molecular mass of 44.8 kDa. There is more than 80% identity between the human and the pig enzymes and also between these enzymes and the F antigen from rat and the two allelic forms of this antigen from mouse. The enzyme has 53% conserved amino a cids and 27% identical amino acids in common with 4-hydroxyphenylpyruv ate dioxygenase from Pseudomonas sp. P. J. 874 and 52% conserved and 2 8% identical residues, with a protein from Shewanella colwelliana. At the C-terminus there is 61% identity between the seven proteins. These results indicate that these proteins are all 4-hydroxyphenylpyruvate dioxygenases. The identity of the C-terminus makes this part of the mo lecule a candidate for a functional role in the catalytic process. At conserved positions in all seven enzymes, there are two tyrosine resid ues and three histidine residues, i. e. amino acids which have been im plicated as ligands for iron in 2-oxoacid-dependent dioxygenases. The gene encoding the enzyme was localized to chromosome 12q14 --> qter by Southern-blot analysis of human-rodent somatic-cell hybrids.