Mammalian liver alcohol dehydrogenases

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Liver alcohol dehydrogenase (ADH) is a critical enzyme involved in alcohol metabolism.
• Understanding ADH properties and isoenzyme variations is essential for comprehending its biological functions.
• Previous research has established basic characteristics of ADH across different species.

Purpose of the Study:

• To review and discuss the physical, chemical, and structural properties of liver alcohol dehydrogenase (ADH) from humans, horses, and rats.
• To explore the structure-function relationships within ADH isoenzymes, focusing on substrate specificity and steroid activity.
• To synthesize current knowledge on ADH properties and isoenzymes for a comprehensive overview.

Main Methods:

• Literature review and comparative analysis of existing studies on liver ADH.
• Discussion of physicochemical properties including molecular weight, subunit composition, catalytic sites, and amino acid composition.
• Examination of X-ray crystallography data for horse liver ADH and analysis of isoenzyme structures and functions.

Main Results:

• Physicochemical properties of human, horse, and rat liver ADH are largely similar, including molecular weight, subunit composition, and zinc metalloenzyme status.
• Horse and human ADH exhibit isoenzyme heterogeneity, with distinct subunits affecting substrate specificity (e.g., steroid activity in some horse ADH variants).
• Rat ADH appears to be a single protein, yet it displays activity with steroids, similar to certain horse liver ADH isoenzymes.

Conclusions:

• Liver ADH enzymes from humans, horses, and rats share fundamental structural and functional similarities.
• Isoenzyme diversity, particularly in horses and humans, leads to varied substrate specificities, including activity towards steroids.
• The physiological significance of steroid activity in ADH remains an open question requiring further investigation.