Skip to main content
Log in

Automethylation of protein (d-aspartyl/l-isoaspartyl) carboxyl methyltransferase, a response to enzyme aging

  • Published:
Journal of Protein Chemistry Aims and scope Submit manuscript

Abstract

A question that is central to understanding the mechanisms of aging and cellular deterioration is whether enzymes involved in recognition and metabolism of spontaneously damaged proteins are themselves damaged, either becoming substrates for their own activity; or being unable to act upon themselves, initiating cascades of cellular damage. We show here byin vitro experiments that protein (d-aspartyl/l-isoaspartyl) carboxyl methyltransferase (PCM) from bovine erythrocytes does methylate age-dependent amino acid damage in its own sequence. The subpopulation that is methylated, termed theαPCM fraction, appears to be formed through age-dependent deamidation of an asparaginyl site to either anl-isoaspartyl ord-aspartyl site because (a) the stoichiometry of automethylation of purified PCM is less than 1%, a value typical of the substoichiometric methylation of many other aged protein substrates, (b)αPCM is slightly more acidic than the bulk of PCM, and (c) the methyl esterified site inαPCM has the characteristic base-lability of this type of methyl ester. Also, the methyl group is not incorporated into the enzyme as an active site intermediate because the incorporated methyl group is not chased onto substrate protein. The effect of enzyme dilution on the rate of the automethylation reaction is consistent with methylation occurring between protein molecules, showing that the pool of PCM is autocatalytic even though individual molecules may not be. The automethylation and possible self-repair of the PCM pool has implications for maintaining thein vivo efficiency of methylation-dependent protein repair.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Similar content being viewed by others

References

Download references

Author information

Authors and Affiliations

Authors

Rights and permissions

Reprints and permissions

About this article

Cite this article

Lindquist, J.A., McFadden, P.N. Automethylation of protein (d-aspartyl/l-isoaspartyl) carboxyl methyltransferase, a response to enzyme aging. J Protein Chem 13, 23–30 (1994). https://doi.org/10.1007/BF01891989

Download citation

  • Received:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/BF01891989

Key words

Navigation