Metabolism coupling agents

Early development of the concept that ATP is a uniquely important metabolic coupling agent was summarized by Lipmann nearly thirty years ago in a classic review [21]. At a time when almost nothing was known about activated intermediates, Lipmann recognized clearly that activation by attachment of groups forming polarized weak bonds must be an essential prerequisite to the metabolic use of many compounds or radicals ... 

Atkinson, D. E., 1971, Adenine nucleotides as imiversal stoichiometric metabolic coupling agents, Adv. Enzyme Regul. 9 207. 

Give the structure of adenosine triphosphate. Describe the role of ATP as the major energy-coupling agent (energy currency) in metabolism. 

Adenine Nucleotides as Stoichiometric Coupling Agents in Metabolism and as Regulatory Modifiers ... 

The coupling of reaction sequences through the adenylate system is entirely different from the two types of stoichiometric relationships discussed above. The stoichiometry of each reaction in which ATP is regenerated or used is, of course, fixed by the nature of the reaction, but the number and types of reactions in which ATP is involved have been determined by evolutionary processes, rather than by simple chemical necessity. Indeed the use of ATP as a coupling agent and the evolutionary adjustments of stoichiometric relationships for maximal metabolic advantage are at the very center of biological function. This fact is underscored by the participation of ATP in every extended metabolic sequence. 

Only the metabolites listed in Table I as coupling agents need be considered at this point others will be discussed in later sections, or in a monograph in preparation. The coupling ratio between ATP regeneration and DPNH oxidation is, of course, the familiar P-O ratio, and a value of 3 is well established for typical eukaryotic cells. The tabulated value of 4 for TPNH may require comment. At least in many types of cells, the TPN system seems to be always far more reduced than the DPN system. In an early review of metabolic functions of... 

A requirement for unacceptably high concentrations of intermediates and coupling agents is avoided in metabolism by the use of activated... 

HMIT is a H+-coupled myo-inositol symporter. High levels of its expression are observed in neurons and glia of hippocampus, hypothalamus, cerebellum and brainstem. Since myo-inositol is a precursor for phosphatidyl inositol, which itself is a critical regulator of many neuronal processes (Ch. 20), HMIT regulation is possibly involved in various mood and behavior patterns that are affected by inositol metabolism and by pharmacologic agents that modify inositol metabolism (see Chs 54 and 55). 

---