Human 4‐hydroxyphenylpyruvate dioxygenase

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Abstract
We report the primary structure of 4‐hydroxyphenylpyruvate dioxygenase [4‐hydroxyphenylpyruvate: oxygen oxidoreductase (hydroxylating, decarboxylating)]. The work is based on the isolation of cDNA clones from human liver λgt11 libraries. Several overlapping clones covering the coding sequence were characterized. In parallel, peptides from four different digests of the purified protein were analysed for their amino‐acid sequence. These peptide sequences covered 86% of the cDNA‐derived 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 acids and 27% identical amino acids in common with 4‐hydroxyphenylpyruvate dioxygenase from Pseudomonas sp. P. J. 874 and 52% conserved and 28% 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 molecule a candidate for a functional role in the catalytic process. At conserved positions in all seven enzymes, there are two tyrosine residues and three histidine residues, i. e. amino acids which have been implicated 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.