Evidence that the human homologue of a rat initiation factor-2 associated protein (p67) is a methionine aminopeptidase.
Previously, we cloned a human cDNA encoding a protein which has a 92% amino acid sequence identity to a rat initiation factor-2 associated protein (p67). Rat p67 plays an important role in translational regulation by preventing the phosphorylation of the alpha subunit of initiation factor-2. Interestingly, several lines of indirect evidence suggested that this protein may also function as a methionine aminopeptidase (MetAP). To test this hypothesis, we expressed the human cDNA in a baculovirus system, purified it to homogeneity and characterized it. Using 13 different peptide substrates, we found that the human p67 has a similar substrate specificity with other MetAPs. Kinetic analyses revealed that the Kcat/K(m) values of the human MetAP on two representative substrates are similar to those of yeast and porcine MetAPs. Furthermore, we found that this enzyme, like other MetAPs, is also a cobalt-dependent metalloenzyme.
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Edward A. Doisy Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, Missouri 63104, USA.
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D000626:Aminopeptidases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D003001:Cloning, Molecular; D018076:DNA, Complementary; D006023:Glycoproteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D063208:Methionyl Aminopeptidases; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D018411:Spodoptera; D013379:Substrate Specificity
D018076:DNA, Complementary; D006023:Glycoproteins; D011994:Recombinant Proteins; D000626:Aminopeptidases; C081311:METAP2 protein, human; C489895:Metap2 protein, rat; D063208:Methionyl Aminopeptidases