Complete nucleotide and deduced amino acid sequence of bovine phenylethanolamine N-methyltransferase: partial amino acid homology with rat tyrosine hydroxylase.

We report here the isolation of a cDNA clone containing the full coding region of bovine phenylethanolamine N-methyltransferase (PNMTase, EC 2.1.1.28, S-adenosyl-L-methionine:phenylethanolamine N-methyltransferase). The complete nucleotide sequence of the cDNA has been determined, and the amino acid sequence of PNMTase deduced. Cultured cells transfected with an expression vector containing this cDNA produced high levels of PNMTase enzymatic activity. Antibodies specific for tyrosine hydroxylase [EC 1.14.16.2, tyrosine 3-monooxygenase; L-tyrosine, tetrahydrobiopterine: oxygen oxidoreductase (3-hydroxylating)], the first enzyme in the catecholamine pathway, possess a striking affinity for the PNMTase protein synthesized in vitro. Comparison of the deduced amino acid sequence of bovine PNMTase to rat tyrosine hydroxylase reveals that PNMTase shares significant homology with tyrosine hydroxylase and supports previous protein and immunological data suggesting that the catecholamine biosynthetic enzymes are structurally related.