The Relation of Insulin to Phosphate Metabolism *

The early work of Embden, Parnas, and others showed that there was an intimate relation between the metabolism of phosphate and carbohydrate in yeast, microorganisms, and mammalian tissues. Since then the field has been expanded until now it includes a fairly comprehensive scheme. A brief epitomization of this scheme is necessary for the understanding of the possible relations of insulin to phosphate metabolism. Strongly schematized, such an epitomization may be divided into two parts: I. Formation of energy-rich phosphate bonds from glycogen, glucose, or other metabolic intermediates. II. Coupling of the metabolism of high-energy phosphate bonds to synthetic, excretory, secretory, absorptive, osmotic, electrical, or mechanical processes. By energy-rich phosphate bond, designated by the sign Ph*, is meant phosphate in such organic combination as creatine phosphate, adenosine tri (or di) phosphate, acetyl phosphate, phosphopyruvate, or other forms not yet recognized. Upon hydrolysis or upon reaction with other substances these compounds regenerate inorganic phosphate with the release of a large amount of free energy, viz: Adenosine triphosphate adenosine diphosphate + H3PO4, -AF 11,000 cals. Such a reaction may be linked by chemical mechanisms, which are in the main part still unknown, to the processes enumerated above to furnish the driving force for them. For example we may picture the following reaction: Ph* + muscle component = Ph + work The currently accepted scheme for the generation of high-energy phosphate from carbohydrate is shown in Table 1. Glycogen takes up phosphate by phosphorolysis, eventually leading to the formation of 6-hexose phosphate according to the scheme of Cori.7 Or glucose, by the forceful introduction of phosphate by adenosine triphosphate (Ph*), forms the same compound. A second forceful