Glycerol as an enzyme-stabilizing agent: effects on aldehyde dehydrogenase

Area of Science:

• Biochemistry
• Enzymology
• Protein Chemistry

Background:

• Yeast potassium-dependent aldehyde dehydrogenase (EC 1.2.1.3) is crucial in metabolic pathways.
• Understanding enzyme behavior in non-aqueous environments is vital for biocatalysis and protein stabilization.

Purpose of the Study:

• To investigate the structural and functional effects of polyhydric alcohols, such as glycerol, on yeast aldehyde dehydrogenase.
• To elucidate the mechanism by which these alcohols stabilize the enzyme and alter its active site properties.

Main Methods:

• Enzyme stability assays under varying glycerol concentrations.
• Kinetic studies measuring K(m) and binding constants for DPN and benzaldehyde.
• Enzyme inhibition studies using trivalent arsenicals (arsenite, Mapharsen).
• Assessment of sulfhydryl group reactivity via carboxymethylation.

Main Results:

• Glycerol (≥30%) significantly enhances enzyme stability during storage and freeze-thaw cycles.
• K(m) for DPN and benzaldehyde binding decreased in glycerol, indicating altered substrate interaction.
• Arsenical inhibition shifted from competitive to mixed, with increased K(i) values, suggesting active site changes.
• Essential sulfhydryl groups became less accessible and reactive in the presence of glycerol and mannitol.

Conclusions:

• Polyhydric alcohols induce conformational changes in yeast aldehyde dehydrogenase, protecting active site sulfhydryl groups.
• These structural alterations enhance enzyme stability and modify substrate and inhibitor binding kinetics.
• The findings highlight the potential of polyhydric alcohols for stabilizing other enzymes and improving their industrial applications.