Carbohydrate Metabolism

Comprehensive Biochemistry, Volume 17: Carbohydrate Metabolism focuses on the processes, reactions, and transformations involved in the metabolism of carbohydrates, including glycosaminoglycans, enzymes, oxidation, and glycolysis.

The selection first elaborates on functional organization contributing to carbohydrate economy and control of synthesis and breakdown of glycogen, starch, and cellulose. Discussions focus on breakdown of glycogen in mammalian systems, role of glycogen in the regulation of glycogen metabolism, glycogen and starch metabolism in bacteria and plants, carbohydrate digestion, and integration of digestion and absorption. The book also ponders on regulation and mechanisms of enzymes and hexose-monophosphate oxidation, including functions and regulation of pentose-phosphate cycle glucose transport and role of subsequent steps in regulating the rate of glycolysis.

The book takes a look at the metabolism of glycosaminoglycans, aldonic and uronic acids, and carbohydrate and oxidative metabolism in neural systems. Concerns include control of carbohydrate metabolism, adaptive changes in relation to carbohydrate metabolism, uronic and aldonic acid metabolism in plants and microorganisms, and mechanism of alternation of monosaccharide units.

The selection is a vital source of data for researchers interested in carbohydrate metabolism.

Contenu

General Preface

Preface to Section IV

Chapter I. Functional Organization Contributing to Carbohydrate Economy

1. Introduction

2. Carbohydrate Digestion

3. Carbohydrate Absorption

   a. Disaccharides

   b. Monosaccharides

   c. Specificity

4. Na+ Interaction with Sugar Transport

5. Integration of Digestion and Absorption

6. Control of Sugar Absorption

   Acknowledgements

   References

Chapter II. Control of Synthesis and Breakdown of Glycogen, Starch and Cellulose

1. Introduction

2. Synthesis of Glycogen in Mammalian Systems

   a. General Background

   b. Synthesis of UDP-D-Glucose

   c. Properties of a-Glucan-UDP-D-Glucose-Glucosyltransferase

   d. Regulation of a-Glucan-UDP-D-Glucose-Glucosyltransferase Activity

   e. Alternative Pathways for Glycogen Synthesis

3. Breakdown of Glycogen in Mammalian Systems

   a. General Properties of a-Glucan(Glycogen) (1 4): Orthophosphate 4-Glucosyltransferase (Phosphorylase)

   b. Allosteric Properties of Muscle Glycogen Phosphorylases

   c. Interconversion of Muscle Phosphorylase b and a

4. The Role of Glycogen in the Regulation of Glycogen Metabolism

   a. Activation of Muscle Phosphorylase a by Glycogen

   b. Molecular Structure of Glycogens

   c. Association of Glycogen with Glycogen-Metabolizing Enzymes

5. Branching and Debranching of Glycogen

   a. Branching Enzymes

   b. Debranching Enzymes

6. Alternative Pathways for the Complete Breakdown of Glycogen

   a. Oligo-a-1,4-Glucan Glucohydrolases

7. Glycogen and Starch-Metabolism in Bacteria and Plants

   a. Control Over the Nucleotide-di-P-Sugar Pool

   b. Synthesis of Starch

8. Metabolism of Glycogen and Trehalose in Insects

9. The Synthesis of Cellulose

10. Concluding Remarks

    Acknowledgement

    References

Chapter III. Glycolysis: Regulation and Mechanisms of the Enzymes

1. Introduction

2. Glucose Transport

3. Phosphorylation of Glucose

   a. Yeast Hexokinase

   b. Mammalian Hexokinase

   c. Regulation of Glucose Utilization by Hexokinases

4. Phosphoglucose Isomerase

   a. Mechanism

   b. Role in Regulation

5. Phosphofructokinase

6. Interlude: Role of Subsequent Steps in Regulating the Rate of Glycolysis

7. Aldolase

   a. Substrate Specificity

   b. Sequence of Reaction

   c. Kinetic Parameters

   d. Mechanism of Aldolase Reaction

   e. Role of Aldolase in Regulation of Glycolysis

8. Triose-P Isomerase

   a. Mechanism

   b. Regulatory Role of Triose-P Isomerase

9. Glyceraldehyde-3-P Dehydrogenase

   Kinetic Studies and Regulation

10. Phosphoglycerate Kinase

    The Role of 3-PGA Kinase in Rate Determination of Glycolysis

11. Phosphoglycerate Mutase

12. Enolase

    a. Yeast Enolase

    b. Muscle Enolase

    c. The Catalytic Reaction

13. Pyruvate Kinase

    a. Reaction and Role in Glycolysis

    b. Muscle Pyruvate Kinase

    c. Molecular Properties

    d. The Catalytic Reaction

    e. Kinetics and Mechanism

    f. Pyruvate Kinase from Other Sources

14. Epilogue

    a. Regeneration of ADP and Pi

    b. Regeneration of NAD+

    c. Intracellular Location of Glycolysis

    References

Chapter IV. Hexose-Monophosphate Oxidation

1. Introduction

2. Glucose-6-Phosphate Dehydrogenase

   a. Human-Erythrocyte Glucose-6-Phosphate Dehydrogenase

   b. Glucose-6-Phosphate Dehydrogenase from Rat-Mammary Gland

   c. Glucose-6-Phosphate Dehydrogenase from Yeast

   d. The Regulation of Glucose-6-Phosphate Dehydrogenase Activity

   e. The Variants of Glucose-6-Phosphate Dehydrogenase

   f. Glucose-6-Phosphate Dehydrogenase Deficiency

3. Lactonase

4. Gluconate-6-Phosphate Dehydrogenase (6-Phospho-D-Gluconate: NADP+ Oxidoreductase, Decarboxylating)

   a. Distribution

   b. Substrate Specificity and Kinetic Properties

   c. Mechanism of the Reaction

   d. Variants of Gluconate-6-Phosphate Dehydrogenase

5. Regulation of the Pentose-Phosphate Cycle

6. Functions of the Pentose-Phosphate Cycle

   a. Utilization of NADPH in Biosynthetic Processes

   b. Production of Pentose and Erythrose

   Acknowledgements

   References

Chapter V. Carbohydrate and Oxidative Metabolism in Neural Systems

1. Introduction

2. Carbohydrate Levels

   a. Methods of Tissue Treatment and Estimation

   b. Glucose

   c. Glycogen

   d. Fructose and Hexose Phosphates

3. Carbohydrate Metabolism

   a. Glycogen Synthesis and Breakdown

   b. Glucose Transport

   c. Glucose Metabolism

   d. Pyruvate Oxidation

4. Environmental Influences

5. Control of Carbohydrate Metabolism

   a. General Considerations

   b. Electrical Stimulation

   c. Ions of External Media and in Cell-Free Systems

   d. Glycolytic Enzymes

6. Adaptive Changes in Relation to Carbohydrate Metabolism

   References

Chapter VI. Aldonic and Uronic Acids

1. Introduction

2. D-Glucuronic Acid and L-Gulonic Acid in Animal Metabolism

   a. D-Glucuronic Acid as a Precursor of L-Ascorbic Acid; L-Gulonic Acid and L-Gulonolactone as Intermediates

   b. D-Glucuronic Acid as a Precursor of L-Xylulose; L-Gulonic and 3-Keto-L-Gulonic Acids as Intermediates

   c. The Overall Utilization of D-Glucuronic Acid

   d. The Metabolic Origin of D-Glucuronic Acid

   e. The Glucuronate-Xylulose Cycle

   f. D-Glucaric Acid as a Metabolic Product of D-Glucuronic Acid

   g. The Catabolism of L-Ascorbic Acid; L-Xylonic and L-Lyxonic Acids as Metabolic Products

3. Other Uronic Acids and Aldonic Acids in Animal Metabolism

   a. D-Galactonic Acid

   b. D-Gluconic Acid

   c. Xylonic Acids

   d. L-Iduronic Acid

4. Uronic and Aldonic Acid Metabolism in Plants and Microorganisms

   a. Uronic Acid Metabolism in Bacteria; Ketouronic and Saccharic Acids

   b. Uronic Acids in Plants

   c. Aldonic and Ketoaldonic Acids in Microorganisms

5. 2-Keto-3-Deoxyaldonic Acids

   a. The Entner-Doudoroff Pathway for Hexose Utilization

   b. Neuraminic Acid Biosynthesis

   c. 2-Keto-3-Deoxyoctonate Biosynthesis

   d. 2-Keto-3-Deoxyaraboheptonic Acid in Biosynthesis of Aromatic Amino Acids

   e. 2-Keto-3-Deoxyarabonic Acid as Intermediate

   References

Chapter VII. The Metabolism of Glycosaminoglycans

1. The Formation of Precursors

…