Chemical modification of yeast 3-phosphoglycerate kinase

Area of Science:

• Biochemistry
• Enzymology

Background:

• Yeast phosphoglycerate kinase is a key enzyme in glycolysis.
• Understanding the role of specific amino acid residues is crucial for enzyme function.

Purpose of the Study:

• To investigate the role of thiol, methionine, tyrosine, and lysine residues in yeast phosphoglycerate kinase activity.
• To determine the impact of chemical modifications on enzyme structure and function.

Main Methods:

• Chemical modification of yeast phosphoglycerate kinase using sulfhydryl reagents, hydrogen peroxide, tetranitromethane, O-methylisourea, 2-methoxy-5-nitrotropone, and pyridoxal phosphate.
• Enzyme activity assays.
• Circular dichroism, spectrofluorescence, and optical rotatory dispersion measurements.

Main Results:

• The thiol group and methionine residues are not essential for enzyme activity.
• Nitration of a single tyrosine residue inhibits enzyme activity, suggesting its importance.
• Chemical modification of lysine residues indicates their essentiality for phosphoglycerate kinase function.
• Substrates offer partial protection against modification of tyrosine and lysine residues.
• Minimal conformational changes were observed upon modification, except for slight spectral changes in some cases.

Conclusions:

• Tyrosine and lysine residues play critical roles in yeast phosphoglycerate kinase activity.
• Enzyme substrates may protect essential residues through conformational changes or direct interaction.
• The enzyme's tertiary structure remains largely intact despite chemical modifications.