Enzymes, Second Edition provides information pertinent to the developments in the field of enzymology. This book presents the properties of enzymes as chemical catalysts or simply as chemical substances.

Organized into 13 chapters, this edition begins with an overview of the range of action or specificity of enzymes. This text then discusses the special techniques employed in the isolation of enzymes and explores the considerable progress in the study of the properties and functions of enzymes. Other chapters consider the mechanism of enzyme catalysis by more direct methods, including the use of isotopes. This book discusses as well the mechanism of the biosynthesis of enzymes and the means by which their chemical structure is determined by the genetic material of the chromosomes. The final chapter deals with the essential aspects of the enzymatic system linking energy-producing processes with energy-utilizing processes.

This book is a valuable resource for biochemists, physical chemists, and research workers.

Preface

I. Introduction


II. Enzyme Techniques


Measurement of Velocity


Classes of Methods


Some Practical Points


The General Handling of Enzymes


The Study of an Enzyme


The Specific and Molecular Activities


Enzyme Affinities


Methods of Quantitatively Following Enzyme Reactions


(a) Spectrophotometric Methods


(b) Manometric Methods


(c) The Thunberg Method


(d) Electrode Methods


(e) Polarimetric Methods


(f) Chromatographic Methods


(g) Chemical Estimations


III. Enzyme Isolation


Importance of Enzyme Purification


Methods of Purification


(a) Test


(b) General Procedure


(c) Source of Enzyme


(d) Extraction


Fractionation Methods


(a) Fractional Precipitation by Change of pH


(b) Fractional Denaturation by Heating


(c) Fractional Precipitation with Organic Solvents


(d) Fractional Precipitation by Salts


(e) Fractional Adsorption


(f) Column Chromatography


(g) Crystallization


(h) Sequence of Fractionation Methods


(i) Other Methods


Criteria of Purity of Enzymes


Pitfalls in Working with Pure Enzymes


IV. Enzyme Kinetics


The Importance of Enzyme Kinetics


Factors Influencing Enzyme Reaction Velocity


(A) Effect of Enzyme Concentration


(B) Effect of Substrate Concentration


(c) Effect of pH


(D) Effect of Temperature


V. Enzyme Classification


Enzyme Commission's Numbering System


Rules for Systematic and Trivial Nomenclatures


(i) General Rules


(ii) Rules for Particular Classes of Enzymes


Enzyme Reactions


1. Oxidoreductases


2. Transferases


3. Hydrolases


4. Lyases


5. Isomerases


6. Ligases


VI. Enzyme Specificity


The Investigation of Enzyme Specificity


General Observations on Specificity


Stereospecificity of Enzymes


Illustrative Examples of Enzyme Specificity


Dehydrogenases


Glucose Oxidase


Methyltransferases


Transketolase and Transaldolase


Glycosyltransferases


Phosphotransferases


Esterases


Phosphatases


Glycosidases


Peptidases


Lyases


Aldose Mutarotase


Enzymes with Substrates Containing Hydrocarbon Chains


General Conclusions


VII. Enzyme Mechanisms


Mechanism of Hydrogen-Transfer Reactions


Alcohol Dehydrogenase


Glyceraldehydephosphate Dehydrogenase


Lipoamide Dehydrogenase


Mechanism of Transferring (or Hydrolysing) Enzymes


(a) Identification of the Bond Affected


(b) Isotope Exchange Methods


(c) The Optical Inversion Method


(d) Inferences from Competition and Other Effects


(e) Identification of Intermediate Complexes


Mechanism of Lyases


Fumarate Hydratase


Aspartate Ammonia-Lyase


Mechanism of Isomerases


Epimerases


Methylmalonyl-CoA Racemase


Cis-trans Isomerases


Ketol-Isomerases


-Isomerases


Methylmalonyl-CoA Mutase


Mechanism of Ligases


Triple-Transfer Mechanism


Ternary Complex Mechanisms


Mechanism of Metalloenzymes


Metal-Activated Peptidases


Zinc-Containing Dehydrogenases


Metalloflavoproteins


Haemoprotein Enzymes


VIII. Enzyme Inhibitors


Types of Inhibitors


Competitive Inhibitors


Non-Competitive Inhibitors


'Mixed-Type' Inhibitors


Graphical Presentation of Inhibitor Effects


Determination of Inhibitor Constants


Other Types of Inhibitors


Inhibitors with Very High Affinities


Effect of pH on Inhibition


Some Important Inhibitors


Poisons of Heavy Metals


Reagents for Thiol Groups


Heavy Metals


Irreversible Organophosphorus Inhibitors


Inhibitors of Respiration and Phosphorylation


Competitive Inhibitors


Antienzymes


IX. Enzyme Cofactors


Specific Coenzymes


Hydrogen Carriers


Lipoate


Glutathione


Ascorbate


Quinones


Cytochromes


Cytochrome Oxidase


Other Hydrogen Carriers


Amino-Group Carriers


2-Oxoglutarate


Phosphate Carriers


Nucleoside 5'-Diphosphates


Mixed Phosphate and Glycosyl Transfers


Acyl-Group Carriers


Coenzyme A


Carriers of One-Carbon Groups


Tetrahydrofolate


Adenosylhomocysteine


Cobamide Coenzymes


Prosthetic Groups as Carriers


Flavin Groups


Pyridoxal Phosphate


Thiamine Pyrophosphate


Biotin


Other Coenzymes


Phosphomutase Coenzymes


Glutathione as a Specific Coenzyme


Relationship Between Coenzymes and Vitamins


Significance of 'Nucleotide' Structure in Coenzymes


Enzyme Activators


Simple Electrolytes


Lipophilic Ions


Polynucleotide Templates


The Distinction Between Prosthetic Group, Coenzyme and Substrate


X. Enzyme Structure


Molecular Weight


Protein Structure


Number of Peptide Chains


Aminoacid Composition


Aminoacid Sequence


Structure and Configuration of the Enzyme Protein


The Chemistry of the Active Centre


Number of Active Centres Per Molecule


Chemical Nature of the Active Centre


XI. Enzyme Formation


The Biosynthesis of Enzymes


Biosynthesis of Proteins


Induction and Repression


Enzyme Formation from Precursors


The Activation of Pepsinogen


The Activation of Prorennin


The Activation of Trypsinogen


The Activation of Chymotrypsinogen


The Activation of Procarboxypeptidases


Activation of the Pancreatic Co…