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Study · Not a test of the peptide alone · 1991

5 results

Optimal conditions for the use of protein L-isoaspartyl methyltransferase in assessing the isoaspartate content of peptides and proteins.

Johnson BA, Aswad DW

Analytical biochemistry1 Feb 1991Cited by 49 (Europe PMC)

PMID1827964 (opens in a new tab)DOI10.1016/0003-2697(91)90553-6 (opens in a new tab)PepBankPUB-01827964
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Summary

The text of this summary is not shown here, because the article license does not allow reuse. Read it at the source (opens in a new tab)

Text rights: Publisher copyright. Results still quote short attributed sentences.

Results from this study5

No result from this study comes from a test of the peptide.

Studies that did not test the peptide alone5

In this study, Delta sleep-inducing peptide (DSIP) was a lab tool or a carrier, part of a mix, or the subject of a lab method. These results are not evidence about taking Delta sleep-inducing peptide (DSIP).

  1. 01LabNot a test of Delta sleep-inducing peptide (DSIP) aloneIn vitro (cell-free)Other

    In an in vitro assay, 1 microM methyltransferase was needed for stoichiometric modification of 2 microM isoaspartyl DSIP in 40-min reactions at pH 6.2 and 30 degrees C.

    In plain wordsIn lab tests, a set amount of enzyme was needed to fully modify isoaspartyl DSIP in an assay.

    Peptide
    Delta sleep-inducing peptide (DSIP)
    Outcome
    Not applicableMethyltransferase concentration needed for stoichiometric modification
    Study

    n: not reported in source

    In vitro methyltransferase assay with isoaspartyl DSIP
    Outcome group
    Analytical methods and detection · Pharmacology

    Measurements

    Methyltransferase concentration required
    1 microM
    2 microM peptide, 40 min, pH 6.2, 30 degrees C

    Source sentences

    Summary
    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.
    1 context sentence
    Summary · context
    To investigate the effects of these conditions, and to optimize the assay, isoaspartyl delta sleep-inducing peptide was methylated under a variety of conditions.

    In this study, Delta sleep-inducing peptide (DSIP) was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Delta sleep-inducing peptide (DSIP).

  2. 02LabNot a test of Delta sleep-inducing peptide (DSIP) aloneIn vitro (cell-free)Other

    In an in vitro assay, carrier protein was necessary for optimal methyltransferase activity at enzyme concentrations below 0.4 microM.

    In plain wordsIn lab tests, a carrier protein was needed for best enzyme activity when little enzyme was present.

    Peptide
    Delta sleep-inducing peptide (DSIP)
    Outcome
    Not applicableCarrier protein requirement at low enzyme concentration
    Study

    n: not reported in source

    In vitro methyltransferase assay with isoaspartyl DSIP
    Outcome group
    Analytical methods and detection · Pharmacology

    Measurements

    Enzyme concentration below which carrier protein is needed
    < 0.4 microM
    methyltransferase

    Source sentences

    Summary
    Carrier protein was necessary for optimal methyltransferase activity at enzyme concentrations below 0.4 microM.

    In this study, Delta sleep-inducing peptide (DSIP) was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Delta sleep-inducing peptide (DSIP).

  3. 03LabNot a test of Delta sleep-inducing peptide (DSIP) aloneIn vitro (cell-free)Other

    In an in vitro assay, 50 microM S-adenosylmethionine was the minimum needed for complete modification of 10 microM peptide.

    In plain wordsIn lab tests, a minimum amount of the methyl donor was needed to fully modify the peptide.

    Peptide
    Delta sleep-inducing peptide (DSIP)
    Outcome
    Not applicableS-adenosylmethionine requirement for complete modification
    Study

    n: not reported in source

    In vitro methyltransferase assay with isoaspartyl DSIP
    Outcome group
    Analytical methods and detection · Pharmacology

    Measurements

    Minimum S-adenosylmethionine concentration
    50 microM
    10 microM peptide

    Source sentences

    Summary
    Stoichiometric methylation required concentrations of S-adenosylmethionine to be in substantial excess over those of peptide; 50 microM S-adenosylmethionine is the minimum needed for complete modification of 10 microM peptide.

    In this study, Delta sleep-inducing peptide (DSIP) was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Delta sleep-inducing peptide (DSIP).

  4. 04LabNot a test of Delta sleep-inducing peptide (DSIP) aloneIn vitro (cell-free)Other

    In an in vitro assay, spontaneous demethylation was significant under all conditions, so the methyl ester never reached 1 mol/mol of total peptide.

    In plain wordsIn lab tests, the added methyl group came off by itself, so the peptide was never fully methylated.

    Peptide
    Delta sleep-inducing peptide (DSIP)
    Outcome
    Not applicableSpontaneous demethylation of the methyl ester
    Study

    n: not reported in source

    In vitro methyltransferase assay with isoaspartyl DSIP
    Outcome group
    Analytical methods and detection · Pharmacology

    Measurements

    Methyl ester ratio reached
    < 1 mol/mol
    total peptide

    Source sentences

    Summary
    Spontaneous demethylation was significant under all conditions tested, so that the methyl ester itself never reached a ratio of 1 mol/mol of total peptide.

    In this study, Delta sleep-inducing peptide (DSIP) was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Delta sleep-inducing peptide (DSIP).

  5. 05Computer modelNot a test of Delta sleep-inducing peptide (DSIP) aloneIn silicoOther

    A computer model using kinetic constants predicted the same methyltransferase concentration requirement for modifying isoaspartyl DSIP.

    In plain wordsA computer model predicted the same enzyme need as the lab tests with isoaspartyl DSIP.

    Peptide
    Delta sleep-inducing peptide (DSIP)
    Outcome
    Not applicablePredicted enzyme requirement from kinetic model
    Study

    n: not reported in source

    Computer kinetic model
    Outcome group
    Analytical methods and detection · Pharmacology

    Source sentences

    Summary
    A computer model utilizing kinetic constants obtained from studies on initial rates of methylation predicted the same requirement for enzyme concentration.
    1 context sentence
    Summary · context
    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.

    In this study, Delta sleep-inducing peptide (DSIP) was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Delta sleep-inducing peptide (DSIP).

AI wrote and checked these results. AI can make mistakes, so check important results against the source.

Version history

PepBank keeps every version of the data on this study. Status changes from Retraction Watch, Europe PMC and Crossref are listed with their source.

  1. Version 2Current

    9 Oct 2026, 18:17 UTC

    Study results updated

  2. Version 1

    9 Oct 2026, 03:04 UTC

    First added · source update from Europe PMC

Subjects

Terms as the source lists them.

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