The Carboxylmethylation of Membrane-Bound Proteins in the Aging Rat Brain
Although the process of cellular aging is admittedly highly complex,  evidence is accumulating to suggest that it has a molecular basis and, hence, that it may be profitably studied through investigations of the aging of intracellular proteins. Several types of modification may be incurred by proteins residing in aging cellular systems [2,3] and part of the relevant research has recently been summarized [4–6]. One type of an enzyme-catalyzed age-related protein modification is its carboxylmethylation. The cognate enzyme, protein carboxylmethyltransferase II (EC. 220.127.116.11) (PCMT). [7,8], appears to recognize only those proteins in which, via biological mechanisms still incompletely understood, [9,10] selected L-aspartate residues have been replaced by D-aspartate [11,12] and/or L- or D-isoaspartate [13–15]. Although several reports associating the presence of protein-bound D-aspartate with aging have appeared, [16–19] there is no unambiguous evidence for the presence of unnatural isoaspartates in proteins of either young or aged cells.
KeywordsSynaptic Membrane Washed Membrane Young Brain Mild Alkali Protein Carboxyl
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