| Preface to the Series | p. iii |
| Preface to Volume 39 | p. v |
| In Memoriam of Professor Robert C. Bray | p. vii |
| Contributors | p. xxiii |
| Contents of Previous Volumes | p. xxvii |
| Handbook on Toxicity of Inorganic Compounds | p. lix |
| Handbook on Metals in Clinical and Analytical Chemistry | p. lix |
| Handbook on Metalloproteins | p. lix |
| The Biogeochemistry of Molybdenum and Tungsten | p. 1 |
| Introduction | p. 2 |
| Molybdenum and Tungsten in the Environment | p. 3 |
| The Nitrogen Cycle | p. 7 |
| Sulfur Metabolism and the Sulfur Cycle | p. 11 |
| Carbon Metabolism | p. 17 |
| Arsenic, Selenium, and Chlorine Metabolism | p. 19 |
| Conclusion | p. 21 |
| Acknowledgment | p. 21 |
| Abbreviations | p. 22 |
| References | p. 23 |
| Transport, Homeostasis, Regulation, and Binding of Molybdate and Tungstate to Proteins | p. 31 |
| Introduction | p. 32 |
| Competition with Iron(III) | p. 34 |
| Transport Systems | p. 39 |
| Cytoplasmic Molybdate-Binding Proteins | p. 49 |
| Conclusions | p. 65 |
| Acknowledgments | p. 67 |
| Abbreviations and Definitions | p. 67 |
| References | p. 68 |
| Molybdenum Nitrogenases: A Crystallographic and Mechanistic View | p. 75 |
| Introduction | p. 76 |
| The Nitrogenases | p. 77 |
| The Molybdenum-Iron Protein | p. 81 |
| The Iron Protein | p. 87 |
| Mechanistic Studies | p. 90 |
| The Nitrogenase Complex | p. 94 |
| The Active Site | p. 98 |
| Conclusions | p. 109 |
| Acknowledgments | p. 110 |
| Abbreviations and Definitions | p. 110 |
| References | p. 111 |
| Chemical Dinitrogen Fixation by Molybdenum and Tungsten Complexes: Insights From Coordination Chemistry | p. 121 |
| Introduction | p. 122 |
| Preparation and Structures of Dinitrogen Complexes | p. 124 |
| Reactions of Coordinated Dinitrogen | p. 130 |
| Conclusions | p. 154 |
| Abbreviations | p. 155 |
| References | p. 155 |
| Biosynthesis of the Nitrogenase Iron-Molybdenum-Cofactor From Azotobacter Vinelandii | p. 163 |
| Introduction | p. 164 |
| Biochemical Genetic Analysis of FeMo Cofactor Biosynthesis | p. 167 |
| A General Model for FeMo Cofactor Biosynthesis | p. 169 |
| Mobilization of Iron and Sulfur | p. 170 |
| NifB Cofactor | p. 171 |
| The NifEN Complex | p. 175 |
| Homocitrate Formation and Molybdenum Insertion | p. 176 |
| Role of Intermediate Carriers in FeMo Cofactor Biosynthesis | p. 179 |
| Role of the Iron Protein in Cofactor Assembly | p. 181 |
| Summary and Future Prospects | p. 182 |
| Acknowledgments | p. 183 |
| Abbreviations | p. 183 |
| References | p. 183 |
| Molybdenum Enzymes Containing the Pyranopterin Cofactor: an Overview | p. 187 |
| Introduction | p. 188 |
| Classification of the Mononuclear Molybdenum Enzymes | p. 195 |
| Consideration of Selected Enzymes Not Covered in Other Chapters | p. 205 |
| Mechanistic Considerations | p. 211 |
| Concluding Remarks | p. 218 |
| Acknowledgment | p. 219 |
| Abbreviations | p. 219 |
| References | p. 219 |
| The Molybdenum and Tungsten Cofactors: A Crystallographic View | p. 227 |
| Introduction | p. 228 |
| Structure of the Mo/W Cofactor | p. 229 |
| Moco-Containing Enzyme Families | p. 232 |
| Limitations of a Crystallographic Model | p. 256 |
| Acknowledgments | p. 258 |
| Abbreviations and Definitions | p. 259 |
| References | p. 260 |
| Models for the Pyranopterin-Containing Molybdenum and Tungsten Cofactors | p. 265 |
| Introduction | p. 266 |
| Early Models | p. 272 |
| Model Complexes of 1,2-Ene-Dithiolates | p. 278 |
| Metal Complexes of Pterins | p. 287 |
| Models with All Three Redox Sites | p. 295 |
| Conclusion | p. 303 |
| Acknowledgments | p. 304 |
| Abbreviations | p. 304 |
| References | p. 305 |
| Biosynthesis and Molecular Biology of the Molybdenum Cofactor (Moco) | p. 317 |
| Introduction | p. 318 |
| Genetics of the Molybdenum Cofactor | p. 322 |
| Biosynthesis of the Molybdenum Cofactor | p. 324 |
| Regulation of Molybdenum Cofactor Synthesis | p. 356 |
| Conclusions | p. 358 |
| Acknowledgments | p. 359 |
| Abbreviations | p. 359 |
| References | p. 359 |
| Molybdenum in Nitrate Reductase and Nitrite Oxidoreductase | p. 369 |
| Introduction | p. 370 |
| Bacterial Respiratory Chains, Metalloenzymes, and Bioenergetics | p. 373 |
| Nitrate Reductase | p. 379 |
| Nitrite Oxidoreductase | p. 391 |
| Environmental Aspects and Biosensors | p. 394 |
| Acknowledgments | p. 395 |
| Abbreviations and Definitions | p. 395 |
| References | p. 396 |
| The Molybdenum-Containing Hydroxylases of Nicotinate, Isonicotinate, and Nicotine | p. 405 |
| Introduction | p. 406 |
| Hydroxylations of Nicotinate and Derivatives | p. 407 |
| Catabolism of Isonicotinate and Derivatives | p. 415 |
| Nicotine Catabolism: Enzymes and Genes Involved in Aerobic Transformations | p. 418 |
| Biotechnological Potentials and Medical Implications | p. 421 |
| Conclusions | p. 423 |
| Acknowledgments | p. 423 |
| Abbreviations | p. 423 |
| References | p. 424 |
| The Molybdenum-Containing Xanthine Oxidoreductases and Picolinate Dehydrogenases | p. 431 |
| Introduction | p. 432 |
| Xanthine Dehydrogenase/Xanthine Oxidase | p. 435 |
| Picolinate Dehydrogenase | p. 447 |
| Conclusions | p. 448 |
| Acknowledgments | p. 449 |
| Abbreviations | p. 449 |
| References | p. 449 |
| Enzymes of the Xanthine Oxidase Family: the Role of Molybdenum | p. 455 |
| Introduction | p. 456 |
| The Reactions Catalyzed | p. 458 |
| Spectroscopic Investigations | p. 462 |
| Kinetic Studies | p. 469 |
| Theoretical Calculations | p. 470 |
| Discussion | p. 472 |
| Conclusions | p. 475 |
| Acknowledgment | p. 475 |
| Abbreviations | p. 475 |
| References | p. 476 |
| The Molybdenum-Containing Hydroxylases of Quinoline, Isoquinoline, and Quinaldine | p. 481 |
| Introduction | p. 482 |
| Biochemical and Genetic Characterization | p. 483 |
| Structural Features of Related Enzymes | p. 494 |
| EPR and ENDOR Characterization of Redox Centers | p. 497 |
| Conclusions | p. 530 |
| Acknowledgments | p. 530 |
| Abbreviations | p. 530 |
| References | p. 531 |
| Molybdenum Enzymes in Reactions Involving Aldehydes and Acids | p. 539 |
| Introduction | p. 540 |
| Enzymes of the Xanthine Oxidase Family | p. 541 |
| Enzymes of the Aldehyde Oxidoreductase Family | p. 559 |
| Conclusions | p. 565 |
| Acknowledgments | p. 566 |
| Abbreviations | p. 566 |
| References | p. 567 |
| Molybdenum and Tungsten Enzymes in C1 Metabolism | p. 571 |
| Introduction | p. 572 |
| Formate Dehydrogenase | p. 575 |
| Formylmethanofuran Dehydrogenase | p. 587 |
| Carbon Monoxide Dehydrogenase | p. 595 |
| Formaldehyde Dehydrogenases | p. 598 |
| Conclusions | p. 601 |
| Acknowledgments | p. 602 |
| Abbreviations and Definitions | p. 602 |
| References | p. 603 |
| Molybdenum Enzymes and Sulfur Metabolism | p. 621 |
| Introduction | p. 622 |
| Sulfite Oxidase | p. 623 |
| Dimethyl Sulfoxide Reductase | p. 635 |
| Biotin Sulfoxide Reductase | p. 642 |
| Polysulfide Reductase | p. 644 |
| Conclusions | p. 645 |
| Acknowledgments | p. 645 |
| Abbreviations and Definitions | p. 646 |
| References | p. 647 |
| Comparison of Selenium-Containing Molybdoenzymes | p. 655 |
| Introduction | p. 656 |
| Overview of Selenium-Containing Molybdoenzymes | p. 658 |
| Incorporation of Selenium into Molybdoenzymes | p. 662 |
| Selenium Versus Sulfur in Catalysis | p. 664 |
| Evolution of Selenocysteine-Containing Molybdoenzymes | p. 667 |
| Conclusions | p. 668 |
| Acknowledgments | p. 669 |
| Abbreviations | p. 669 |
| References | p. 670 |
| Tungsten-Dependent Aldehyde Oxidoreductase: A New Family of Enzymes Containing the Pterin Cofactor | p. 673 |
| Introduction | p. 674 |
| Classification of Tungstoenzymes | p. 677 |
| Aldehyde Ferredoxin Oxidoreductase | p. 680 |
| Carboxylic Acid Reductase and Aldehyde Dehydrogenase | p. 685 |
| Formaldehyde Ferredoxin Oxidoreductase | p. 687 |
| Glyceraldehyde-3-Phosphate Ferredoxin Oxidoreductase | p. 690 |
| Hypothetical Tungstoenzymes--WOR4 and WOR5 | p. 691 |
| Tungsten Versus Molybdenum in the AOR Family | p. 692 |
| Conclusions | p. 693 |
| Acknowledgment | p. 694 |
| Abbreviations | p. 694 |
| References | p. 695 |
| Tungsten-Substituted Molybdenum Enzymes | p. 699 |
| Introduction | p. 700 |
| Molybdenum and Tungsten Chemistry: Similarities and Differences | p. 701 |
| Molybdenum and Tungsten Geochemistry and Link to Bioavailability | p. 704 |
| Early Attempts to Substitute Tungsten for Molybdenum | p. 705 |
| Tungsten-Substituted Molybdenum Enzymes | p. 707 |
| Molybdenum-Substituted Tungsten Acetylene Hydratase | p. 719 |
| Conclusions | p. 720 |
| Abbreviations | p. 721 |
| References | p. 722 |
| Molybdenum Metabolism and Requirements in Humans | p. 727 |
| Introduction | p. 728 |
| Essentiality of Molybdenum in Humans | p. 728 |
| Dietary Intake and Bioavailability of Molybdenum | p. 729 |
| Molybdenum Deficiency and Toxicity | p. 731 |
| Stable Isotope Studies of Molybdenum Metabolism | p. 733 |
| Conclusions | p. 736 |
| Abbreviations | p. 736 |
| References | p. 736 |
| Metabolism and Toxicity of Tungsten in Humans and Animals | p. 741 |
| Introduction | p. 742 |
| Metabolism of Tungsten | p. 742 |
| Toxicity of Tungsten | p. 752 |
| Conclusions | p. 755 |
| Abbreviations and Definitions | p. 755 |
| References | p. 756 |
| Subject Index | p. 761 |
| Table of Contents provided by Syndetics. All Rights Reserved. |
