QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ghandour, H. Articles by Selhub, J. Search for Related Content PubMed PubMed Citation Articles by Ghandour, H. Articles by Selhub, J.

---

Nutrition and Aging
Research Communication

Folate Status and Age Affect the Accumulation of L-Isoaspartyl Residues in Rat Liver Proteins^{1 ,2}

Vitamin Metabolism, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111 and ^* Department of Agricultural Chemistry, College of Agriculture, National Taiwan University, Taipei, Taiwan 10764, Republic of China

³To whom correspondence should be addressed. E-mail: jselhub{at}hnrc.tufts.edu.

Formation of atypical L-isoaspartyl residues in proteins and peptides is a common, spontaneous and nonenzymatic modification of aspartyl and asparaginyl sites. The enzyme protein-L-isoaspartyl methyltransferase (PIMT) catalyzes the transfer of the methyl group of S-adenosyl-L-methionine (SAM) to these L-isoaspartyl sites, thereby allowing reisomerization and restoration of the original alpha peptide linkage. Because SAM is in part a product of folate metabolism, the present study was undertaken to determine the effects of folate deficiency on the presence of L-isoaspartyl residues in hepatic proteins. Young (weanling) and older (12 mo) Sprague-Dawley rats were fed a folate-sufficient (2 mg folate/kg diet) or folate-deficient (0 mg folate/kg diet) diet for 20 wk. Liver proteins were analyzed for L-isoaspartyl residues. This analysis was based on the PIMT-dependent incorporation of [³H]-methyl groups from [³H]-SAM and the subsequent (nonenzymatic) sublimation of these methyl groups into a nonaqueous scintillant. The amount of L-isoaspartyl residues in hepatic proteins was higher in younger folate-deficient than in folate-sufficient rats (deficient: 187 ± 71, sufficient: 64 ± 43 pmol/mg protein, P < 0.025). This difference, however, was not seen among the older groups of rats who instead exhibited a much larger accumulation of L-isoaspartyl residues in their hepatic proteins (deficient: 528 ± 151, sufficient: 470 ± 204 pmol/mg protein, P = 0.568). The importance of these observations is discussed.

KEY WORDS: • folate • L-isoaspartyl • S-adenosyl-L-methionine • protein L-isoaspartyl methyltransferase • rats

This article has been cited by other articles:

				H. Jang, J. B. Mason, and S.-W. Choi Genetic and Epigenetic Interactions between Folate and Aging in Carcinogenesis J. Nutr., December 1, 2005; 135(12): 2967S - 2971S. [Abstract] [Full Text] [PDF]