Part I General Aspects of Nucleotide Metabolism 1

1 Structures of Nucleotide-Related Compounds 3

1.1 Introduction 3

1.2 Nomenclature and Abbreviations of Nucleotide-Related Compounds 3

1.3 Chemical Structures of Nucleotide-Related Compounds 5

1.4 Summary 11

References 11

2 Occurrence of Nucleotides and Related Metabolites in Plants 13

2.1 Purines and Pyrimidines 13

2.2 Pyridine Nucleotides 17

2.3 Concentration of Cytokinins 18

2.4 Alkaloids Derived from Nucleotides 18

2.5 Summary 19

References 19

3 General Aspects of Nucleotide Biosynthesis and Interconversions 21

3.1 Introduction 21

3.2 De Novo Biosynthesis of Ribonucleoside Monophosphates 21

3.3 Interconversion of Nucleoside Monophosphates, Nucleoside Diphosphates, and Triphosphates 23

3.4 Conversion of Nucleoside Diphosphates to Nucleoside Triphosphates 24

3.5 Biosynthesis of Deoxyribonucleotides 29

3.6 Nucleic Acid Biosynthesis 29

3.7 Supply of 5-Phosphoribosyl-1-Pyrophosphate 30

3.8 Supply of Amino Acids for Nucleotide Biosynthesis 33

3.9 Nitrogen Metabolism and Amino Acid Biosynthesis in Plants 33

3.10 Summary 34

References 35

Part II Purine Nucleotide Metabolism 39

4 Purine Nucleotide Biosynthesis De Novo 41

4.1 Introduction 41

4.2 Reactions and Enzymes 43

4.3 Summary 52

References 52

5 Salvage Pathways of Purine Nucleotide Biosynthesis 55

5.1 Introduction 55

5.2 Characteristics of Purine Salvage in Plants 56

5.3 Properties of Purine Phosphoribosyltransferases 59

5.4 Properties of Nucleoside Kinases 62

5.5 Properties of Nucleoside Phosphotransferase 65

5.6 Role of Purine Salvage in Plants 66

5.7 Summary 66

References 66

6 Interconversion of Purine Nucleotides 71

6.1 Introduction 71

6.2 Deamination Reactions 71

6.3 Dephosphorylation Reactions 75

6.4 Glycosidic Bond Cleavage Reactions 76

6.5 In Situ Metabolism of 14C-Labelled Purine Nucleotides 79

6.6 In Situ Metabolism of Purine Nucleosides and Bases 80

6.7 Summary 88

References 89

7 Degradation of Purine Nucleotides 95

7.1 Introduction 95

7.2 (S)-Allantoin Biosynthesis from Xanthine 97

7.3 Catabolism of (S)-Allantoin 101

7.4 Purine Nucleotide Catabolism in Plants 106

7.5 Accumulation and Utilization of Ureides in Plants 107

7.6 Summary 111

References 111

Part III Pyrimidine Nucleotide Metabolism 117

8 Pyrimidine Nucleotide Biosynthesis De Novo 119

8.1 Introduction 119

8.2 Reactions and Enzymes of the De Novo Biosynthesis 121

8.3 Control Mechanism of De Novo Pyrimidine Ribonucleotide Biosynthesis 127

8.4 Biosynthesis of Thymidine Nucleotide 129

8.5 Summary 131

References 131

9 Salvage Pathways of Pyrimidine Nucleotide Biosynthesis 137

9.1 Introduction 137

9.2 Characteristics of Pyrimidine Salvage in Plants 137

9.3 Enzymes of Pyrimidine Salvage 139

9.4 Role of Pyrimidine Salvage in Plants 145

9.5 Summary 146

References 146

10 Interconversion of Pyrimidine Nucleotides 149

10.1 Introduction 149

10.2 Deaminase Reactions 149

10.3 Nucleosidase and Phosphorylase Reactions 152

10.4 In Situ Metabolism of 14C-Labelled Pyrimidines 153

10.5 Summary 159

References 160

11 Degradation of Pyrimidine Nucleotides 165

11.1 Introduction 165

11.2 Enzymes Involved in the Degradation Routes of Pyrimidines 166

11.3 The Metabolic Fate of Uracil and Thymine 168

11.4 Summary 169

References 170

Part IV Physiological Aspects of Nucleotide Metabolism 173

12 Growth and Development 175

12.1 Introduction 175

12.2 Embryo Maturation 175

12.3 Germination 180

12.4 Organogenesis 185

12.5 Breaking Bud Dormancy 186

12.6 Fruit Ripening 186

12.7 Storage Organ Development and Sprouting 186

12.8 Suspension-Cultured Cells 187

12.9 Molecular Studies 189

12.10 Summary 189

References 189

13 Environmental Factors and Nucleotide Metabolism 195

13.1 Introduction 195

13.2 Effect of Phosphate on Nucleotide Metabolism 195

13.3 Effect of Salts on Nucleotide Metabolism 199

13.4 Effect of Water Stress 202

13.5 Effect of Wound Stress 202

13.6 Effect of Iron Deficiency 205

13.7 Effect of Light 206

13.8 Summary 206

References 206

Part V Purine Alkaloids 211

14 Occurrence of Purine Alkaloids 213

14.1 Introduction 213

14.2 Chemical Structure of Purine Alkaloids 213

14.3 Occurrence of Purine Alkaloids in Plants 215

14.4 Summary 226

References 226

15 Biosynthesis of Purine Alkaloids 231

15.1 Introduction 231

15.2 A Brief History of Caffeine Biosynthesis Research 231

15.3 Caffeine Biosynthesis Pathway 234

15.4 Genes and Proteins of Caffeine Synthase Family 245

15.5 Xanthosine Biosynthesis from Purine Nucleotides 249

15.6 Summary 253

References 253

16 Physiological and Ecological Aspects of Purine Alkaloid Biosynthesis 259

16.1 Introduction 259

16.2 Physiology of Caffeine Biosynthesis 259

16.3 Subcellular Localization of Caffeine Biosynthesis 268

16.4 Regulation of Caffeine Biosynthesis 270

16.5 Ecological Roles of Caffeine 271

16.6 Summary 274

References 275

17 Metabolism of Purine Alkaloids and Biotechnology 281

17.1 Introduction 281

17.2 Metabolism of Purine Alkaloids 281

17.3 Diversity of Purine Alkaloid Metabolism in Plants 285

17.4 Biotechnology of Purine Alkaloids 293

17.5 Caffeine-Producing Transgenic Plants 295

17.6 Summary 298

References 298

Part VI Pyridine Nucleotide Metabolism 301

18 Pyridine (Nicotinamide Adenine) Nucleotide Biosynthesis De Novo 303

18.1 Introduction 303

18.2 Two Distinct Pathways of De Novo Nicotinate Mononucleotide Biosynthesis 303

18.3 The Outline of the De Novo Pathway of NAD Biosynthesis in Plants 304

18.4 Enzymes Involved in De Novo NAD Synthesis in Plants 307

18.5 Summary 310

References 310

19 Pyridine Nucleotide Cycle 315

19.1 Introduction 315

19.2 Pyridine Nucleotide Cycle 315

19.3 Catabolism of NAD 320

19.4 Enzymes Involved in NAD Catabolism 321

19.5 Salvage of Nicotinamide and Nicotinate 323

19.6 Summary 325

References 325

Part VII Pyridine Alkaloids 329

20 Occurrence and Biosynthesis of Pyridine Alkaloids 331

20.1 Introduction 331

20.2 Occurrence of Pyridine Alkaloids 333

20.3 Biosynthesis of Pyridine Alkaloids 335

20.4 Summary 345

References 345

21 Physiological Aspect and Biotechnology of Trigonelline 351

21.1 Introduction 351

21.2 Physiological Aspect of Trigonelline Biosynthesis 351

21.3 Physiological Aspect of Nicotinate N-Glucoside Biosynthesis 356

21.4 The Role of Trigonelline in Plants 356

21.5 Biotechnology of Trigonelline 360

21.6 Summary 362

References 363

Part VIII Other Nucleotide-Related Metabolites 367

22 Sugar Nucleotides 369

22.1 Introduction 369

22.2 The Sugar Nucleotide Moiety 370

22.3 Enzymes of Sugar Nucleotide Biosynthesis 371

22.4 Localization of UDP-Glucose-Producing Enzymes 377

22.5 UDP-Glucose-Interconversion 377

22.6 Other Metabolites 379

22.7 Summary 382

References 382

23 Cytokinins 387

23.1 Introduction 387

23.2 Adenosine Phosphate-Isopentenyl Formation 388

23.3 trans-Zeatin Phosphate Synthesis 389

23.4 Formation of Cytokinin Bases 389

23.5 Effect of Nucleotide Enzymes in Cytokinins 390

23.6 New Purine-Related Plant Growth Regulators 392

23.7 Summary 393

References 394

Part IX Dietary Plant Alkaloids, Their Bioavailability, and Potential Impact on Human Health 397

24 Bioavailability and Potential Impact on Human Health of Caffeine, Theobromine, and Trigonelline 399

24.1 Caffeine 399

24.2 Theobromine 404

24.3 Trigonelline 406

24.4 Summary 409

References 409

Index 415