Publisher Summary The interaction of proteins with small ligands embodies the fundamental physicochemical principles that are operative in the physiological regulation of enzyme activity, the specific interactions among proteins and of proteins with nucleic acids and other macromolecules. This chapter describes the multiple ligand binding by proteins, binding by multimer proteins, extension of the concept of ligand interaction to covalent bond exchange, cooperativity and ligand correlation, and biological specificity and ligand binding. Many parts of the compact protein structure can contribute toward the shift in energy and structure taking place on ligand binding. The energies of ligand–ligand interaction, although small are sufficient to shift the covalent equilibria in which proteins take part, to a significant extent, and this may be found responsible for the interconversion of chemical and osmotic energies in metabolism. While, the ligand correlation because of the existence of free-energy coupling among the bound ligands is a molecular property to be explained by a study of the isolated protein, the enhancement of the effects by the simultaneous changes in ligand concentration is a system property that requires consideration of other entities. The consideration of ligand–protein interactions provides with a model for the relative importance to be assigned to molecules in the organic functions. Thus, study of the interactions of proteins and small ligands provides the basis for the understanding of biological specificity at the molecular level.

Energetics of Ligand Binding to Proteins

Publisher Summary This chapter describes the hormonal control of hepatic gluconeogenesis, which is the process whereby lactate, pyruvate, glycerol, and certain amino acids are converted into glucose and glycogen. The liver is the major site of gluconeogenesis although the kidney becomes important during prolonged starvation. The most important function of gluconeogenesis is the maintenance of blood glucose levels during times when food intake is restricted and/or glycogen stores are depleted. Hormonal control of gluconeogenesis can be divided for convenience into three categories. The first involves the regulation of substrate supply. All gluconeogenic substrates reach the liver in subsaturating concentration. Thus, the regulation of substrate release into the blood from the extrahepatic tissues will directly affect hepatic glucose formation. The regulation of the level of cyclic AMP (cAMP) could also explain the inhibitory effect of insulin on gluconeogenesis. There is also evidence that insulin can suppress gluconeogenesis by a mechanism that is independent of changes in cAMP.

Hormonal control of hepatic gluconeogenesis.

El nombre actual de la revista es FEBS Journal: Open Access para articulos anteriores al 2006.-- Autores pertenecientes al extinto Instituto de Enzimologia del CSIC.

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Conformational changes in the allosteric inhibition of muscle pyruvate kinase by phenylalanine.