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Optimal Conditions for the Use of Protein L-isoaspartyl Methyltransferase in Assessing the Isoaspartate Content of Peptides and Proteins by Brett A. Johnson; Dana W. Aswad is a Biochemistry, Genetics and Molecular Biology article available to read on EtoBox.
What is Optimal Conditions for the Use of Protein L-isoaspartyl Methyltransferase in Assessing the Isoaspartate Content of Peptides and Proteins about?
Protein L-isoaspartyl methyltransferase provides a basis for enzymatic measurement of atypical, isoaspartyl linkages which make a major contribution to protein microheterogeneity. The low Vmax of the methyltransferase reaction and the instability of the methyl ester can hinder accurate determinations, and different laboratories using different conditions have achieved discrepant values for the isoaspartate content of the same proteins. To investigate the effects of these conditions, and to optimize the assay, isoaspartyl delta sleep-inducing peptide was methylated under a variety of conditions. We found that 1 microM methyltransferase was required to obtain stoichiometric modification of 2 microM peptide in 40-min reactions at pH 6.2 and 30 degrees C. A computer model utilizing kinetic constants obtained from studies on initial rates of methylation predicted the same requirement for enzyme concentration. Carrier protein was necessary for optimal methyltransferase activity at enzyme concentrations below 0.4 microM. Stoichiometric methylation required concentrations of S-adenosylmethionine to be in substantial excess over those of peptide; 50 microM S-adenosylmethionine is the minimu
Who reads Optimal Conditions for the Use of Protein L-isoaspartyl Methyltransferase in Assessing the Isoaspartate Content of Peptides and Proteins?
It is typically read by researchers, students, and practitioners in Biochemistry, Genetics and Molecular Biology.
- Author
- Brett A. Johnson; Dana W. Aswad
- Publisher
- Elsevier Science; Elsevier ; Elsevier Inc.; Elsevier BV (ISSN 0003-2697)
- Published
- 1991
- Language
- EN
- Field
- Biochemistry, Genetics and Molecular Biology (Life Sciences)