The action of the couple ascorbic acid--Cu(II) on NAD(+)-coenzymatic function

Area of Science:

• Biochemistry
• Free Radical Chemistry

Background:

• Nicotinamide adenine dinucleotide (NAD+) is a crucial coenzyme in metabolic processes.
• Its coenzymatic function can be compromised by oxidative stress.
• Ascorbic acid-Cu(II) systems are known generators of free radicals.

Purpose of the Study:

• To investigate the degradation of NAD+ by free radicals generated from the ascorbic acid-Cu(II) system.
• To identify factors influencing this degradation process.
• To evaluate the protective effects of various antioxidant compounds against NAD+ damage.

Main Methods:

• Incubation of NAD+ with the ascorbic acid-Cu(II) system under varying conditions (buffer, pH, temperature, time).
• Assessment of NAD+ degradation by measuring the release of breakdown products.
• Testing the efficacy of antioxidants such as thiourea, potassium iodide (IK), glutathione (GSH), cysteine, mannitol, and albumin.

Main Results:

• The ascorbic acid-Cu(II) system significantly reduces the coenzymatic capacity of NAD+.
• Degradation is influenced by buffer type, pH, temperature, and incubation duration.
• Thiourea, IK, GSH, cysteine, mannitol, and albumin offered varying degrees of protection against radical-induced NAD+ damage.
• NAD+ degradation involves the cleavage of ester and anhydride bonds, releasing nicotinamide riboside and nicotinamide ribonucleotide, along with orthophosphate.

Conclusions:

• Free radicals generated by the ascorbic acid-Cu(II) system actively degrade NAD+.
• The extent of NAD+ degradation is modulated by environmental factors and the presence of specific chemical agents.
• Certain compounds can act as scavengers, protecting NAD+ from oxidative damage, highlighting potential therapeutic or preventative strategies.