An iron-activated alcohol dehydrogenase.

Area of Science:

• Biochemistry
• Enzymology
• Microbial Physiology

Background:

• Alcohol dehydrogenase (ADH) is crucial for ethanol fermentation in Zymomonas mobilis.
• The cofactor requirements of Zymomonas mobilis ADH are not fully understood.
• Metal-complexing agents can inactivate enzymes, necessitating studies on cofactor restoration.

Purpose of the Study:

• To investigate the metal ion activation of alcohol dehydrogenase from Zymomonas mobilis.
• To determine the physiological role of metal ions in Zymomonas mobilis ADH activity.
• To explore the kinetic properties of the iron-activated enzyme.

Main Methods:

• Enzyme purification and isolation of alcohol dehydrogenase from Zymomonas mobilis.
• Enzyme inactivation using metal-complexing agents.
• Re-activation assays with various metal ions (ferrous, zinc, cobaltous).
• Kinetic analysis of the iron-reconstituted enzyme.

Main Results:

• Alcohol dehydrogenase was inactivated by metal-complexing agents.
• Ferrous ions effectively re-activated the enzyme, while zinc ions did not.
• Cobaltous ions showed a lesser re-activating effect.
• Kinetic studies revealed an 'alcohol activation' phenomenon in the iron-treated enzyme.

Conclusions:

• Zymomonas mobilis alcohol dehydrogenase likely utilizes iron as a natural cofactor.
• The observed iron-dependent activation and kinetic properties suggest a mechanism to overcome product inhibition during fermentation.