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Contents XI

15.2.1 Coupling with Other Enzymes as Auxiliary Agents 317
15.2.1.1 Coupling with NAD(H)-Dependent Dehydrogenases 317
15.2.1.2 Coupling with Bovine Serum Albumin 319
15.2.1.3 Coupling with BSA and Polyphenol Oxidase 321
15.2.2 Coupling with a Nonprotein Auxiliary Agent 325
15.2.2.1 Chemoenzymatic Cascade Reaction Based on Redox
Chromophore 325
15.2.2.2 Phenol Red as pH Indicator 326
15.3 Cascade Reactions for Assaying Transketolase Activity by In Vivo
Selection 329
15.3.1 Biocatalyzed Synthesis of Probes 16a,b 330
15.3.2 In Vitro Studies with Wild-Type TK and Probes 16a,b by LC/MS 330
15.3.3 Detection of TK Activity in E. coli Auxotrophs from Amino Acid
Precursors 331
15.4 Conclusion 334
References 335

16 Aldolases as Catalyst for the Synthesis of Carbohydrates and
Analogs 339
Pere Clap´es, Jes´us Joglar, and Jordi Bujons
16.1 Introduction 339
16.2 Iminocyclitol and Aminocyclitol Synthesis 340
16.3 Carbohydrates and Other Polyhydroxylated Compounds 351
16.4 Conclusions 355
Acknowledgments 356
References 356
17 Enzymatic Generation of Sialoconjugate Diversity 361
Wolf-Dieter Fessner, Ning He, Dong Yi, Peter Unruh, and Marion Knorst
17.1 Introduction 361
17.2 A Generic Strategy for the Synthesis of Sialoconjugate Libraries 363
17.2.1 Synthesis of Sialic Acid Diversity 368
17.2.1.1 Neuraminic Acid Aldolase 368
17.2.1.2 Neuraminic Acid Synthase 371
17.2.2 Nucleotide Activation of Sialic Acids 372
17.2.2.1 Kinetics of Sialic Acid Activation 373
17.2.2.2 Substrate Binding Model 373
17.2.2.3 Engineering of Promiscuous CSS Variants 376
17.2.3 Sialic Acid Transfer 377
17.3 Cascade Synthesis of neo-Sialoconjugates 378
17.3.1 Choice of Sialyl Acceptor 378
17.3.2 One-Pot Two-Step Cascade Reactions 379
17.3.3 One-Pot Three-Step Cascade Reactions 383
17.3.4 Metabolic Diversification 385
17.3.5 Post-Synthetic Diversification 386