Current Topics in Cellular Regulation

List of Contributors

Preface

Conformational Aspects of Enzyme Regulation

I. Introduction

II. The Symmetry Model

III. The Ligand-Induced or Sequential Model

IV. Comparison of the Models

V. Observed Systems

VI. Evaluation

VII. Future Developments

References

Limitation of Metabolite Concentrations and the Conservation of Solvent Capacity in the Living Cell

I. Introduction

II. Activated Forms of Intermediates

III. Levels of Enzyme Activities

IV. Michaelis Constants

V. Modulation of Enzyme Activity

VI. Summary

The Role of Equilibria in the Regulation of Metabolism

I. Introduction

II. The Role of the Lactate Dehydrogenase System in the Control of Gluconeogenesis from Lactate

III. The Role of Equilibria in the Alcohol Dehydrogenase System in the Metabolism of Ethanol

IV. Extrahepatic Ketogenesis

V. Equilibria in the Metabolism of Propionate

VI. Summing Up

References

Regulation of the Biosynthesis of the Branched-Chain Amino Acids

I. Historical Introduction

II. Regulation of Metabolite Flow by End-Product Inhibition

III. Control of Enzyme Level in the Pathways to the Branched-Chain Amino Acids

IV. The Inhibition of Growth of Escherichia coli Strain K12 by Valine

References

On the Roles of Synthesis and Degradation in Regulation of Enzyme Levels in Mammalian Tissues

I. Introduction

II. Properties of Protein Turnover in Rat Liver

III. Theoretical Formulation of a Model for Changing Enzyme Levels in Animal Tissues

IV. Control of Synthesis and Degradation of Specific Enzymes

V. On Mechanisms Controlling Synthesis and Degradation of Specific Enzymes

VI. Concluding Remarks

References

The Regulation of the Biosynthesis of α-1,4-Glucans in Bacteria and Plants

I. Introduction

II. Properties of the ADP-Glucose:α-1,4-Glucan-4-Glucosyl Transferases of Plants

III. Glycogen Accumulation in Bacteria

IV. Bacterial ADP-Glucose : α-1,4-Glucan-4-Glucosyl Transferases

V. ADP-glucose Pyrophosphorylase (Synthetase)

VI. Kinetic Properties of the ADP-Glucose Pyrophosphorylase

VII. Physical Properties of the ADP-Glucose Pyrophosphorylases

VIII. Genetic Regulation of Glycogen Synthesis in Escherichia coli

References

Allosteric L-Threonine Dehydrases of Microorganisms

I. Introduction

II. Biodegradati ve Dehydrase of Escherichia coli

III. Biodegradative Dehydrase of Clostridium tetanomorphum

IV. Biosynthetic L-Threonine Dehydrases

V. Conclusion

References

The Aspartokinases and Homoserine Dehydrogenases of Escherichia coli

I. Two Aspartokinases in Escherichia coli

II. The Threonine-Sensitive Homoserine Dehydrogenase of Escherichia coli

III. Isolation of a Mutant Lacking the Lysine-Sensitive Aspartokinase Gif 54 and of Revertants Thereof

IV. Inhibition Properties of the Aspartokinase and of the Homoserine Dehydrogenase of the Threonine-Excreting Revertants of Gif 54

V. Mutants Lacking Homoserine Dehydrogenase in Escherichia coli B

VI. Indirect Evidence That the Threonine-Sensitive Aspartokinase and Homoserine Dehydrogenase of Escherichia coli K12 Are Carried by the Same Molecule

VII. Direct Evidence That the Threonine-Sensitive Aspartokinase and Homoserine Dehydrogenase of Escherichia coli K12 Are Carried by the Same Protein

VIII. Determination of the Molecular Weight of Aspartokinase I-Homoserine Dehydrogenase I

IX. Amino Acid Analysis of Aspartokinase I-Homoserine Dehydrogenase I

X. Subunit Structure of Aspartokinase I-Homoserine Dehydrogenase I

XI. The Binding of Threonine to Aspartokinase I-Homoserine Dehydrogenase I

XII. The Binding of Pyridine Nucleotides of Aspartokinase I-Homoserine Dehydrogenase I

XIII. The Effects of Threonine on Aspartokinase I-Homoserine Dehydrogenase I Are Not Due Only to Direct Interaction

XIV. Aspartokinase I-Homoserine Dehydrogenase I and the Transconformation Models

XV. Demonstration of the Existence in Escherichia coli K12 of a Third Aspartokinase and of a Second Homoserine Dehydrogenase (Aspartokinase II and Homoserine Dehydrogenase II), Two Activities under the Repressive Control of Methionine

XVI. Indirect Evidence for a Single Protein Carrying the Aspartokinase and Homoserine Dehydrogenase II Activities in Escherichia coli K12

XVII. The Situation in Escherichia coil B as Opposed to E. coli K12

XVIII. Direct Evidence That Aspartokinase II and Homoserine Dehydrogenase II Activities Are Carried by the Same Protein. Its Molecular Weight and Subunit Structure

XIX. Discussion on the Origin of the Two Multifunctional Proteins and of Aspartokinase III. Antigenic Independence of the Three Proteins

XX. The Significance of Iso functional and Multifunctional Enzymes in the Regulation of Biosynthetic Pathways

References

Pyruvate Dehydrogenase Complex

I. Introduction

II. Composition and Macromolecular Organization

III. Regulatory Features

IV. Significance of Multienzyme Complexes in Cellular Regulation

References

Pyruvate Carboxylase

I. Introduction. The Discovery and Metabolic Roles of Pyruvate Carboxylase

II. Mechanism of Action

III. Structure

IV. Role of Acetyl-CoA in the Pyruvate Carboxylate Reaction

V. Conclusion. Regulation of Pyruvate Carboxylase by Mechanisms Not Related to the Concentration of Acetyl-CoA

References

Author Index

Subject Index