Regenerating liver in aged rats produces unaltered phosphoglycerate kinase.

Pure phosphoglycerate kinase from old rat liver shows altered properties. However, when old animals are partially hepatectomized, the regenerating liver produces the "young" form of the enzyme. By 4 or 5 days after hepatectomy, the enzyme once again becomes "old" in its properties. The results are interpreted as showing that normal enzyme is produced that becomes post-synthetically modified. This interpretation agrees with the idea that in old animals, "young" enzymes become conformationally modified, perhaps because of a slowing of protein turnover.