Altered phosphoglycerate kinase in aging rats.

Area of Science:

• Biochemistry
• Aging Research
• Enzymology

Background:

• Phosphoglycerate kinase (PGK) is a crucial enzyme in glycolysis.
• Investigating age-related changes in enzyme properties is vital for understanding aging.
• Previous studies suggest enzymes may undergo alterations with age.

Purpose of the Study:

• To compare the properties of phosphoglycerate kinase (PGK) from young and old rat muscle.
• To identify age-related alterations in enzyme structure and function.
• To investigate the tissues affected by these age-related changes.

Main Methods:

• Enzyme isolation and purification from young and old rat muscle.
• Assays for enzyme stability (heat, storage), reactivity of sulfhydryl (-SH) groups, and UV spectroscopy.
• Immunotitration using antisera against young PGK.
• Analysis of N-terminal and C-terminal amino acid sequences.
• Isoelectric focusing to detect charge alterations.

Main Results:

• Old rat muscle PGK exhibited greater stability to heat and storage compared to young PGK.
• The sulfhydryl (-SH) group of old PGK reacted slower, and its UV spectrum was altered.
• Immunotitration revealed age-related alterations in liver and brain PGK, but not in kidney, lung, or heart.
• N-terminal and C-terminal analyses showed no loss of amino acids; both forms had blocked N-termini and identical C-terminal sequences (Ala-Val-Leu-COOH).
• Isoelectric focusing did not detect deamidation or other charge differences.

Conclusions:

• Muscle phosphoglycerate kinase (PGK) undergoes age-related conformational alterations in old rats.
• These changes affect enzyme stability and reactivity without altering catalytic activity (Km, specific activity).
• The observed alterations are tissue-specific, impacting liver and brain PGK more than others.