Fundamentals of Biochemistry - A. A. Anisimov 1986

Biological Oxidation and Bioenergetics
The Development of the Theory of Biological Oxidation

The works of Russian scientists A. N. Bakh (1897) and V. I. Palladin (1907) played a crucial role in developing The Theory of Biological Oxidation. From a chemical standpoint, Respiration is a slow oxidation process. Hydrogen or electrons are transferred from a donor DH₂ to an acceptor A:

Class="center">ДН₂ + А ⇄ Д + АН₂

The donor is oxidized, and the acceptor is reduced. In The final stage of oxidation-reduction reactions, hydrogen combines with oxygen:

Н₂ + ¹/₂О₂ → Н₂О

Under normal conditions, this reaction occurs instantaneously and is accompanied by such a massive release of energy that an explosion takes place. During respiration, The transport of hydrogen and electrons from one carrier to another occurs stepwise, through a series of intermediate reactions. As a result, the energy of oxidation is released in small, manageable portions and stored in high-energy compounds. This process can involve the activation of either the substrate-bound hydrogen or molecular oxygen from the air.

It is well known that molecular oxygen has a relatively low reactivity. A. N. Bakh's theory was based on the premise that molecular oxygen can act as an oxidizing agent for organic substances only after being activated by the Cleavage of one of the bonds in its molecule. Such activation occurs, in particular, when easily oxidizable compounds—such as those containing double bonds—are present in the medium. By interacting with oxygen, they form peroxides:

These peroxides subsequently oxidize other molecules. Thus, oxidation proceeds via The formation of peroxides as intermediate products:

In these reactions, oxidation proceeds concurrently and interdependently with reduction. A. N. Bakh was the first to articulate METABOLISM/2.html">THE CONCEPT OF coupled oxidation-reduction processes in respiration. According to Bakh, oxidation mediated by peroxides during respiration takes place with the participation of the enzyme peroxidase. Collectively, his concepts became known as Bakh's peroxide theory of respiration.

The works of V. I. Palladin also made a major contribution to The Development of the theory of biological oxidation. He advanced the view of respiration as a system of enzymatic processes, placing special emphasis on The oxidation of respiratory substrates through the removal of hydrogen.

According to Palladin, glucose oxidation occurs in two phases:

Anaerobic phase: С₆Н₁₂О₆ + 6Н₂О + 12R → 6СО₂ + 12RH₂       (1)

Aerobic phase: 12RH₂ + 6О₂→ 12R + 12Н₂О   (2)

In these equations, R represents pigments or chromogens, i.e., intermediate hydrogen carriers.

Subsequent research explored the relationship between respiration and other metabolic processes, the Properties of Enzymes catalyzing BIOLOGICAL OXIDATION REACTIONS, their intracellular localization, and the mechanisms of energy accumulation and transformation, among other topics. Major contributions to these studies in the USSR were made by V. A. Engelhardt, V. A. Belitser, S. E. Severin, V. P. Skulachev, and others, while internationally, key figures included H. Wieland, O. Warburg, D. Keilin, H. Krebs, A. Lehninger, P. Mitchell, D. Green, B. Chance, and E. Racker.