Aging and accuracy of protein synthesis in man: search for inactive enzymatic cross-reacting material in granulocytes of aged people.

Enzyme activities and immunological reactivities of seven different enzymes have been assayed in the polymorphonuclear leukocytes from 10 newborns, 10 aged (over 80 years old) and 10 young adults (20-30 years old). Polymorphonuclears have been chosen because both in the newborns, and in the aged people, they are young cells whose life span is a few hours only. Five cytoplasmic enzymes have been immunologically studied by means of monospecific antienzyme sera: leukocyte pyruvate kinase by immunoinactivation, glucose-6-phosphate dehydrogenase and glucose phosphate-isomerase by electroimmunodiffusion, lactic dehydrogenase (muscle-type) by radial immunodiffusion. Two lysosomal enzymes (alpha-mannosidase and beta-glycuronidase) have been titrated immunologically with the same polyvalent antihuman leukocyte rabbit serum. Small but significant differences in activity were observed for several of the enzymes. By contrast, no significant difference was found, for any of the seven enzymes, as regards the ratio enzyme activity/immunological reactivity, between newborns, young adults and aged people. These results of not support the theory that a decreased accuracy of the protein synthesis machinery is responsible for aging and death. By contrast, the authors emphasize that the enzyme abnormalities reported by various authors in old animals or in old fibroblast cultures closely resemble those demonstrated to be "post-translational modifications" in the case of human glucose-6-phosphate dehydrogenase.