J. Biol. Chem., Vol. 255, Issue 11, 5043-5050, Jun, 1980

Altered phosphoglycerate kinase in aging rats

HK Sharma, HR Prasanna and M Rothstein

Pure phosphoglycerate kinase from young and old rat muscle shows substantial differences in properties. Compared to the "young" enzyme, phosphoglycerate kinase isolated from old animals possesses a greater stability to heat and storage, a slower reacting -SH group, an altered UV spectrum, and requires more antiserum prepared to "young" enzyme for 50% inactivation. Km and specific activity are unchanged. Immunotitration experiments show evidence for an age-related alteration of the enzyme in liver and brain, but not in kidney, lung, or heart. Loss of NH2- or COOH-terminal amino acids is not responsible for the observed differences in the properties of "young" and "old" muscle phosphoglycerate kinase. Both forms of the enzyme contain a blocked (presumably acylated) NH2-terminal residue and the sequence of the three COOH-terminal residues (Ala-Val-Leu-COOH) is identical. Moreover, isoelectric focusing of the two enzyme forms of both acrylamide gels and in a sucrose gradient failed to detect evidence of deamidation or other charge-altering differences. We conclude that, like enolase from aged nematodes, muscle phosphoglycerate kinase becomes altered in conformation in old rats.
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