Relationship between enzymatic activity loss and post-translational protein modification in aging

Area of Science:

• Biochemistry
• Gerontology
• Molecular Biology

Background:

• Enzyme activity declines with age, but the underlying mechanisms remain unclear.
• Investigating age-related changes in enzyme function is crucial for understanding aging processes.

Purpose of the Study:

• To elucidate the molecular mechanisms behind the decreased activity of malic enzyme, 6-phosphogluconate dehydrogenase, and superoxide dismutase during aging.
• To identify specific chemical modifications in these enzymes that correlate with age-associated functional decline.

Main Methods:

• Enzyme activity assays were performed on young and old enzyme preparations.
• Chemical modification studies using diethyl pyrocarbonate and 2,4,6-trinitrobenzenesulfonic acid.
• Proteolytic digestion with trypsin and endoproteinase Arg-C.
• Oxidative stress induction using ascorbate treatment.

Main Results:

• Old malic enzyme showed reduced activity (36%) and a loss of histidine residues compared to young enzyme.
• Old 6-phosphogluconate dehydrogenase exhibited decreased activity (26%) and fewer lysine residues.
• Ascorbate treatment mimicked some age-related changes, causing loss of activity and amino acid residues.
• Superoxide dismutase also showed age-related modifications, likely due to oxidation.

Conclusions:

• Histidine modification may contribute to malic enzyme activity loss in aging.
• Lysine modification is implicated in the reduced activity of 6-phosphogluconate dehydrogenase during aging.
• Oxidative modification of amino acid residues appears to be a significant factor in age-related enzyme dysfunction.