Mechanism of inactivation and identification of sites of modification of ornithine aminotransferase by 4-aminohex-5-ynoate.
The inactivation of ornithine aminotransferase by an enzyme-activated irreversible inhibitor 4-aminohex-5-ynoate was accompanied by stoichiometric binding of the radiolabeled compound. Distribution of radiolabel among separated tryptic peptides indicated that more than one amino acid residue had reacted. Lys-292 and Cys-388 were positively identified. Reduction with borohydride was necessary to stabilize the adduct formed with Lys-292, and the relevant peptide prepared after this treatment contained equimolar amounts of inhibitor and coenzyme. The coenzyme chromophore in this peptide showed strong negative circular dichroism. A mechanism consistent with these observations is proposed.
De Biase
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Department of Biochemistry, University of Wales College of Cardiff, United Kingdom.
Simmaco
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Barra
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Bossa
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Hewlins
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John
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RA
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000614:Aminocaproates / Q000378:metabolism / Q000494:pharmacology*; D001665:Binding Sites; D002942:Circular Dichroism; D007700:Kinetics; D009953:Ornithine-Oxo-Acid Transaminase / Q000037:antagonists & inhibitors*; D010446:Peptide Fragments / Q000302:isolation & purification; D011485:Protein Binding; D011489:Protein Denaturation; D014357:Trypsin; D020888:Vigabatrin
D000596:Amino Acids; D000614:Aminocaproates; D010446:Peptide Fragments; D009953:Ornithine-Oxo-Acid Transaminase; D014357:Trypsin; D020888:Vigabatrin