[Reversible electric current generation by reconstituted mitochondrial transhydrogenase]

Area of Science:

• Biochemistry
• Molecular Biology
• Bioenergetics

Context:

• Mitochondrial transhydrogenase is vital for cellular redox balance and energy production.
• Understanding its electrogenic properties is key to elucidating its physiological role.
• Previous studies lacked direct electrophysiological measurements of the purified enzyme.

Purpose:

• To directly measure the electrogenic activity of purified mitochondrial transhydrogenase.
• To investigate the relationship between transhydrogenase reaction direction and electric potential generation.
• To establish a functional assay for reconstituted transhydrogenase.

Summary:

• Beef heart mitochondrial transhydrogenase was isolated and reconstituted into proteoliposomes.
• These proteoliposomes were incorporated into a phospholipid-impregnated membrane filter.
• Addition of substrates for both forward (NADPH/NAD+) and reverse (NADH/NADP+) reactions induced an electric potential difference across the membrane, with the direction dependent on the reaction.
• The proteoliposome-supplemented compartment charged negatively during the reverse reaction.
• The membrane retained electrogenic capability even after removing excess proteoliposomes.

Impact:

• Provides direct evidence of mitochondrial transhydrogenase's electrogenic function.
• Offers a novel method for studying enzyme activity and membrane potential.
• Enhances understanding of mitochondrial bioenergetics and redox homeostasis.