A peptide inhibitor for S-adenosyl-l-methionine-dependent transmethylation reactions: Purification and characterization |
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| Institution: | 1. Laboratory of Translational Genomics, Centre for Integrative Biology, University of Trento, Italy;2. Center of Physiopathology of Human Reproduction, Unit of Obstetrics and Gynecology, IRCCS A.O.U. San Martino IST, Genoa, Italy;3. Neuroblastoma Laboratory, Pediatric Research Institute, Fondazione Città della Speranza, Padua, Italy |
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| Abstract: | - 1.1. A proteinaceous inhibitor for S-adenosyl-l-methionine (AdoMet)-dependent transmethylation reactions has been purified to apparent homogeneity from rat liver cytosolic fraction.
- 2.2. The peptide was made up of 29 amino acid residues with a molecular weight of 2,584. Glycine accounted for 52% of the total amino acids.
- 3.3. Employing AdoMet: protein-carboxyl O-methyltransferase (Protein methylase II) and bovine serum γ-globulin as in vitro substrate, the mode of inhibition was found to be non-competitive with Ki value of 1.9 × 10?8 M.
- 4.4. When the inhibitor was present in the reaction mixture together with S-adenosyl-l-homocysteine (AdoHcy), which is a competitive inhibitor for AdoMet, the extent of inhibition exceeded that exerted by each individual inhibitor alone, suggesting that the sites of the inhibitors on the enzyme molecule are different.
- 5.5. Almost a stoichiometric relationship exists between the enzyme and the inhibitor molecule, the ratio being approx one.
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