Amphibolic

The term amphibolic is used to describe a biochemical pathway that involves both catabolism and anabolism.

This term was proposed by B.Davis in 1961 to emphasise the dual metabolic role of such pathway. The citric acid cycle (The Krebs Cycle) is a good example of amphibolic pathway. The first reaction of the cycle, in which oxaloacetate (a four carbon compound) condenses with acetate (a two carbon compound) to form citrate (a six carbon compound) is typically anabolic. The next few reactions, which are intramolecular rearrangements, produce isocitrate. The following two reactions are typically catabolic. COO is lost in each step and succinate (a four carbon compound) is produced.

There is an interesting and critical difference in the coenzymes used in catabolic and anabolic pathways; in catabolism NAD+ serves as an oxidizing agent when it is reduced to NADH. Whereas in anabolism the coenzyme NADPH serves as the reducing agent and is converted to its oxidized form NADP+.