PMID:2018773
| Citation |
Diaz, E and Anton, DL (1991) Alkylation of an active-site cysteinyl residue during substrate-dependent inactivation of Escherichia coli S-adenosylmethionine decarboxylase. Biochemistry 30:4078-81 |
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| Abstract |
S-Adenosylmethionine decarboxylase from Escherichia coli is a member of a small class of enzymes that uses a pyruvoyl prosthetic group. The pyruvoyl group is proposed to form a Schiff base with the substrate and then act as an electron sink facilitating decarboxylation. We have previously shown that once every 6000-7000 turnovers the enzyme undergoes an inactivation that results in a transaminated pyruvoyl group and the formation of an acrolein-like species from the methionine moiety. The acrolein then covalently alkylates the enzyme [Anton, D. L., & Kutny, R. (1987) Biochemistry 26, 6444]. After reduction of the alkylated enzyme with NaBH4, a tryptic peptide with the sequence Ala-Asp-Ile-Glu-Val-Ser-Thr-[S-(3-hydroxypropyl)Cys]-Gly-Val-Ile-Ser-Pro - Leu-Lys was isolated. This corresponds to acrolein alkylation of a cysteine residue in the second tryptic peptide from the NH2 terminal of the alpha-subunit [Anton, D. L., & Kutny, R. (1987) J. Biol. Chem. 262, 2817-2822]. The modified residue derived is from Cys-140 of the proenzyme [Tabor, C. W., & Tabor, H. (1987) J. Biol. Chem. 262, 16037-16040] and lies in the only sequence conserved between rat liver and E. coli S-adenosylmethionine decarboxylase [Pajunen et al. (1988) J. Biol. Chem. 263, 17040-17049]. We suggest that the alkylated Cys residue could have a role in the catalytic mechanism. |
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| Keywords |
Adenosylmethionine Decarboxylase/antagonists & inhibitors; Alkylation; Amino Acid Sequence; Binding Sites; Carbon Radioisotopes; Cysteine; Escherichia coli/enzymology; Kinetics; Molecular Sequence Data; Peptide Fragments/isolation & purification; S-Adenosylmethionine/metabolism; S-Adenosylmethionine/pharmacology; Schiff Bases; Spectrometry, Mass, Fast Atom Bombardment; Trypsin |
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