Isbn 0854046917

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Preface

"It is from the behaviour of simple molecules that we learn our most significant lessons."

Sir Frederick Gowland Hopkins, 1913

This book arose out of a course of lectures I was invited to give to young post-graduate students at Universidade Federal de Alagoas, Maceio, Brazil in 1999. Students working on practical aspects of insect pest control through the use of natural pesticides, pheromones and hormones need to know something about the origin of these substances in nature, if they are to use their skills fully in their work. There is not much information available to them in a clear and elementary form in the review literature or books, so I undertook to provide them with an introductory guide to biosynthetic pathways, with special emphasis on insects. I have subsequently expanded the notes prepared for them to make this small book, with the hope that it will prove useful and informative not only to them but to other students in science and technology, and perhaps attract more of them to this interesting and growing area of chemical ecology.

Where biosynthetic processes differ between animals and plants or micro-organisms, I have concentrated on animal systems, but I have not confined myself strictly to the Insecta. The close interaction between plants and insects makes it necessary at times to look at plant substances and pathways, and I have, where important or interesting examples present themselves from other areas, strayed to other arthropods, and even man to complete the story

Because this is intended as a didactic work for young students, I have not used the apparatus of references as in a scholarly review. Experience has shown me that faced with many references to research literature, they may consult none of them. I have rather referred in the text to a few especially useful or interesting papers, and added a list of further reading at the end of each chapter. I have also included a few problems so that readers can make a self-assessment of their grasp of what has been discussed.

Acknowledgements

I am grateful to my friends Neil Oldham, John Brand, Ralph Howard, Athula Attygalle, Graeme Jones and Désiré Daloze for reading various parts or drafts and giving me many helpful suggestions, and to Jane Parker for giving me a student view on an early draft. The request for the original lectures came from my former student Ruth do Nascimento, to whom I am much indebted. I thank the British Council office in Recife, and CNPQ for the financial support that enabled me to give the lectures, and Professor Antonio Euzébio G. Sant'Ana for his hospitality. I am very grateful to Dr John Shanklin of Brookhaven National Laboratory and Dr Ed Cahoon of the Danforth Plant Sciences Center for kindly providing the diagrams of castor oil desaturase, Prof John Mann and Dr Rishuo Nishida for permission to use figures from their work. I am obliged to Dr Jonathan Banks in Australia and Dr Keith S. Brown in Brazil for helping me concerning the final position of aphinin research.

Those of us laboratory-bound do not get to see a great variety of insects in their natural surroundings. I can happily thank various friends for contributing their photographs of (biosynthetically) interesting insects. Stefano Turillazzi, Università di Firenze, for his picture of Polistes wasps, Athulla Attygalle and Maria Eisner for Epilachnis pupae, Steve McWilliam of rECOrd, Chester, for Coccinella septempunctata adults and Jim Klaisch of the Department of Entomology, University of Nebraska - Lincoln for the C. septempunctata larva, Dr Mike Quinn, Texas A&M University, Stephenville, for superb pictures of Hippodamia, Oncopeltus and Danaus, Tom Larsen for Scolopendra, Jens Christian Schou for Arctia caja, Warren E. Savary for Lytta magister, Markku Savela for Harpaphe haydeniana, Dr Hamish Robertson of the South African Museum for Ceroplastes, Dr Paul Choate, Department of Entomology and Nematology, University of Florida for Manduca sexta larva, Société Nouvelle des Éditions Boubée for permission to reproduce the photo of a female silk moth taken by Jacques Six, Anthony Papadoupolos for the fire bug Pyrrhcorus apterus, the University of Oklahoma Veterinary School for Amblyomma americanum, and our own Terry Bolam for the Myrmica ant trail-following. The cover photo is one of the many beautiful insect photos taken by Ken Preston-Mafham of Premaphotos Wildlife. I have tried to find the owner of the picture of the cheese mite, Tyrophagus putrescentiae without success.

I have sought to locate owners of all reproduced material not in my own possession. In a few cases I have been completely unsuccessful, but trust I have not inadvertently infringed any copyrights. Should I have done so I shall of course take appropriate action for any subsequent editions. I would also welcome comments and suggestions on this book, (e. d. [email protected] keele. ac.uk)

Contents

Chapter 1 Introduction 1

1.1 The Structures of Natural Products 2

1.2 Compounds and Function 2

1.3 Studying Biosynthetic Pathways 5

1.4 Plant Versus Insect Biosynthesis 6

1.5 Arthropods and Insects 7 Background and Further Reading 9 Questions 9

Chapter 2 Enzymes and Coenzymes 10

2.1 The Chemical Reactivity of Enzymes 10

2.1.1 Lysozyme 10

2.1.2 Carboxypeptidase 12

2.1.3 Cytochromes

2.2 Coenzymes 13

2.2.1 Coenzyme A 14

2.2.2 Nicotinamide Adenine Dinucleotide 15

2.2.3 Flavin Adenine Dinucleotide 16

2.2.4 Thiamine Diphosphate 17

2.2.5 Tetrahydrofolic Acid 19

2.2.6 S-Adenosylmethionine 19

2.2.7 Pyridoxal Phosphate 19

2.2.8 Vitamins 21

2.2.9 Biosynthesis of Formic Acid in Ants 21

2.3 Pyruvic Acid 22

2.4 Chirality 23 2.4.1 Asymmetric Induction 24 Background and Further Reading 26 Questions

Chapter 3 Fatty Acids and Derived Compounds 28

3.1 Fatty Acids 28

3.1.1 Biosynthesis 29

3.1.2 Unsaturated Acids and Desaturase Enzymes

3.1.3 Eicosanoids

3.1.4 Branched Fatty Acids

3.2 Cuticular Hydrocarbons

3.2.1 Hydrocarbon Pheromones

3.3 Lepidopteran Sex Pheromones

3.4 Coleoptera

3.4.1 Coccinellines

3.4.2 Epilachnine

3.5 Cockroaches

3.6 Termites

3.7 Honeybees

3.8 Ants

3.9 Spiders

3.10 Hemiptera

3.10.1 Green Leaf Volátiles

3.11 Lactones

Background and Further Reading Questions

Chapter 4 Polyketides and Acetogenins

4.1 Acetogenins

4.2 Polyketide Derivatives

4.3 Volatile Pheromones 4.3.1 Cyclic Ketals

4.4 Defensive Secretions Background and Further Reading Questions

Chapter 5 Experimental Methods

5.1 Tracing Biosynthetic Pathways

5.1.1 Specific Incorporation

5.1.2 Locating the Site of Synthesis

5.2 Radio-isotope Labelling 5.2.1 Examples

5.3 Heavy Isotope Labelling

5.3.1 Examples

5.3.2 Carpophilus Beetle Pheromone

5.3.3 13C-13C Coupling

5.4 Isotope Effects

5.4.1 Kinetic Isotope Effects

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