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Fundamentals of enzymology? Fundamentals of Enzymology

by Nicholas C. Price and Lewis Stevens, Oxford University Press, 1982. £25.00 (hardback)/£12.50 (paperback) (xvi + 454 pages) ISBN 0 198 57175 5 (hardback)/ISBN 0198 57176 3 (paperback) The authors state that the intentions of this book are to give a broad account of enzymology and to discuss the properties of enzyme systems of increasing complexity, from isolated enzymes to enzymes within the cell. It is intended for undergraduates reading biochemistry and related biological sciences, and an elementary knowledge of biochemistry is assumed. It is disappointing that a book with these aims pays rather little attention to several aspects that many would regard as being fundamental to any understanding of the behaviour of enzymes. Thus, only four pages are devoted to the measurement of the transient phases of enzyme-catalysed reactions, and the kinetics of enzymes that use more than one substrate and the effects of pH on enzyme activity are dealt with in similarly short sections. With such a degree of economy it is perhaps not surprising that the description and analysis in these sections is superficial. For example the account of the effects of pH on enzyme activity only considers the effects on the maximum velocity, because 'Kin is a function of several rate constants'; there is no mention of the effects of V]Km. In contrast, a chapter of some 70 pages deals with general aspects of protein chemistry, including the determination of molecular size, amino-acid composition, sequence and quaternary structure. Even here, however, some topics, such as X-ray crystallography and the determination of enzyme structure in solution, are described only briefly and in terms that are too general to provide much information. The material presented in this chapter repeats that found in many standard undergraduate textbooks on biochemistry, although it does deal with some aspects in rather more depth. The space devoted to these aspects at the expense of topics such as those mentioned earlier is surprising in a book specifically on enzymes. Because of this lack of balance this book cannot be recommended as giving a broad account of the fundamentals of enzymology. It fact its strengths lie more in the areas of metabolism and its regulation. There are good chapters on the regulation of enzyme activity by allosteric and covalent modification, the properties of organized enzyme systems, and the hehaviour of enzymes within the cell. Well-chosen examples of

the individual enzymes and enzyme systems are discussed in some detail to illustrate the theoretical points that are made, and in these as in other chapters the quite extensive reference lists contain a good halance between monographs, reviews and original research papers. A full chapter is devoted to the turnover of enzymes within the cell, a topic which is too often ignored. There is a good chapter on the mechanism of enzyme action, which briefly outlines the general principles before giving detailed accounts of individual enzymes for which plausible mechanisms have been proposed. This approach allows the authors logically to present the experimental evidence that has led to the proposed mechanisms and to demonstrate the specific features of each mechanism. The use of several examples is, however, less successful in the chapter on enzyme purification. The methods that may be used are discussed rather too briefly, and the remainder of the chapter is devoted to quite detailed descriptions of the published procedures for the purification of six different enzymes. The

examples chosen do not, in my view, adequately illustrate the full range of approaches that have been used and the ingenuity that has been applied in different cases. The chapter might have benefited from more detailed accounts of the methods involved, including dye-ligand chromatography and the use of immobilized antibodies, and the principles behind them, at the expense of at least some detailed examples. The book concludes with chapters on clinical aspects of enzymology and enzyme technology. These chapters are clearly presented although somewhat lacking in detail. I would have liked to see some discussion on the effects of immobilization on enzyme properties in the latter chapter and a more detailed account of enzyme-linked immunoassay in the former. In summary, because of its lack of balance, this book could not be recommended as fulfilling the promise of its title but it does contain much that students would benefit from reading. KEITH TIPTON

Keith Tipton is at the Department of Biochemistry, Trinity College, Dublin 2, Ireland.

Mixed bag on mixed cultures Mixed Culture Fermentations (Special Publications of the Society for General Microbiology, Vol. 5)

edited by M. E. Bushell and J. H. Slater, Academic Press, 1981. £12.00/$25.00 (xi + 175pages) ISBN 0121 47480 1 Microbial Interactions and Communities, Vol. 1

edited by A. T. Bull and J. H. Slater, Academic Press, 1982. £33.80/$69.50 (i + 567pages) 1SBN 0 121 40301 7 It seems appropriate to review together these two books from Academic Press which have in common the same joint editor in the person of J. H. Slater, and a similar theme, namely, the characterization of mixed populations of micro-organisms and the interactions occurring between them. The publication of these two books reflects the now very substantial interest among microbiologists concerning both the theoretical and applied aspects of this complex area of microbiology. Although written around the theme of microbial interactions, these two books emphasize different aspects of the subject; they are also quite dissimilar with respect to size, method of production, and consequently price. Mixed Culture Fermentations, a rather slim volume in camera-ready typescript,

consists of reviews based on papers given at a Symposium of the Society for General Microbiology, in December 1980. As its title suggests, this book falls squarely into the area of biotechnology and provides up-to-date information on a number of traditional processes as well as descriptions of several novel processes currently under development. After a useful conceptual opening chapter by Slater, there is a creditable attempt by Bazim to describe some of the current approaches to the study of microbial interaction kinetics. Unfortunately there is no easy way to present this information and most microbiologists will founder among the multiplicity of equations. Two useful chapters follow dealing with the microbiology of waste treaWnent processes. Much has already been written about this area of microbiology but Hobson on anaerobic digesters and Somerville on aerobic processes have usefully presented the information in terms of microbial ecology, and have expounded the importance and nature of the metabolic interactions between different micro-organisms which form the essence of these processes. The dairy industry represents another area in which mixed culture processes have traditionally been operated; as an example Driessen gives a detailed account of yoghurt production and describes in particular recent research to develop a continuous

TIBS - March 1983

114 manufacturing process. The presence of mixed cultures in fermentations is of course not always beneficial, and White and Kidney discuss beer spoilage problems which appear to arise because of aggregation between brewing yeasts and spoilage bacteria. Also writing in the realm of the traditional processes, Wood, on the basis one suspects of many years of reflection, presents his ideas on the special nature of yeast/lactobacillus associations which occur in a remarkably diverse range of food and beverage fermentations. The final chapter by Lee reflects the more modern era of biotechnology and gives an account of certain algal-bacterial consortia which, it is proposed, could be used for the photosynthetic production of biomass. Altogether this is a useful and interesting book; for £ 12 it is well worth recommending to libraries. Publishing books from conference proceedings can, however, impose certain limitations on content. A more comprehensive coverage to include topics such as the potential of mixed cultures for solid-state fermentation of lignocellulosic materials and for ethanol and the production of single-cell protein would have made this a more important book. The more recently published Microbial Interactions and Communities is a much more substantial book and certainly more appealing in terms of paper and print quality. There are 13 chapters of which (apart from the In'st two 'introductory' type chapters by the editors) eight are concerned essentially with ecological topics and three with technological applications. Each chapter has an extensive bibliography for those researching in these areas. The first of the two chapters by Bull and Slater gives an account of the historical background to the pure-culture concept and it contains some fascinating details of the early era of microbiology. The second chapter by the editors is concerned mainly with the problems and approaches to classifying the various categories of microbial interactions. Two chapters are then devoted to describing experimental methodologies which is fitting since improvements in techniques have played a key role in advancing our understanding of microbial interactions. Parkes covers laboratory methods in a comprehensive review, and Fry describes and comments on the various approaches to analysing microbial communities in situ. Several very interesting chapters then follow dealing with interactions between particular groups of micn~ organisms. Kuenen and Gottschal describe mainly competitions which occur between heterotrophic bacteria and chemolithotrophs (or is it chemoautotrophs or even chemolithoautotrophs!). Jones then pre-

sents a fascinating account of the interactions between algae and bacteria, a topic for which such a review was badly needed. Cairns describes what has been done to characterize protozoan communities and in his concluding section predicts that interest in these and other microbial communities is likely to grow in the near future. One reason put forward is that such research may be a suitable surrogate for the more expensive research on larger organisms for which funding may not be so readily available as it has been in the past. Microbiologists these days seem to be getting favours from all directions! The importance of genetic interactions has not been overlooked in this book, and a broad-ranging chapter is presented by Reanney et al. which considers the evidence for such interchange and its actual or potential importance in host-pathogen interactions as well as in natural ecosystems. Two other ecological-type chapters deal with the utilization of particular substrates by mixed, microbial populations. Wolin discusses the production and utilization of hydrogen from a variety of substrates in anaerobic microbial ecosystems, and Burns presents a major and stimulating review of carbon mineralization by mixed populations. The applied dimension in the book comes in the form of three technologically orientated chapters. The f'trst of these, by Linton and Drozd, deals with the potential

uses of mixed cultures in biotechnological processes with particular emphasis on single-cell protein and ethanol production. In a chapter on the use of micro-organisms for metal recovery, mainly by acid leaching, Norris and Kelly discuss the probable potential, although as yet lack of understanding, of the role of microbial interactions in these processes. A synthesis o f geography and microbiology is presented by Steinkraus who describes the role of mixed cultures in the production of a diverse range of fermented foods and beverages from an equally diverse range of countries. The ample evidence provided in this chapter of the numerous ways in which mixed cultures have already been exploited should encourage the modern biotechnologists' belief that surely at least a few more must be possible. Although this is not a cheap book, nevertheless it is comprised of an excellent series of chapters which together provide a unique coverage of this important area of microbiology. It can be thoroughly recommended and should be on the shelves of all libraries which wish to keep abreast of developments in microbiology. The book's title specifies this text as Volume 1 and it is to be hoped that additional volumes devoted to this theme will follow. J. G. ANDERSON J. G. Anderson is at the Department of Bioscience and Biotechnology, Universi~ of Strathclyde, Glasgow G1 1XW, U.K.

Stimulating thoughts on theoretical bioenergetics Energy Metabolism of the Cell - A Theoretical Treatise by J. G. Reich and E. E. Sel'kov, Academic Press, 1981. £36.00/$74.00 (viii + 345pages) I S B N 0125 859201

The study of metabolism is often considered as old-fashioned and is viewed by many students as a list of successive interconversions of molecules in the living cell. This view would be somewhat equivalent to assuming that a road map gives an accurate description of the road traffic; indeed a quantitative description of the traffic requires a knowledge of the numbers of cars on the motorways and roads, the cars' average speeds, etc. Similarly a coherent view of metabolism requires a knowledge of the dynamics of molecules along the metabolic pathways. The aim of this book by Reich and Sel'kov is precisely to present energy metabolism as a dynamic and functional unit. The living cell is envisaged as an open reactor containing a network of metabolic reactions.

For about 20 years, the regulation of metabolic circuits has often been explicitly or implicitly considered as being exerted by the remarkable and complex properties of a rather small number of 'regulatory' or 'allosteric' enzymes. Although the role played by these enzymes is no doubt important, this reductionist way of depicting metabolic regulation is somewhat nai've and inadequate. One of the leitmotivs of the present book is to show that the main dynamic properties of metabolic circuits, namely homeostasis and adaptability, do not rely on the sensing properties of some complex 'allosteric' enzymes, but are rather the natural properties Of the reaction network as a whole. Interconnecting enzyme reactions and an analysis of the behaviour of the network thus formed, together with the formalism of control system theory, allow us to predict remarkable properties of this system - properties that seem to be 'novel' with respect to those of the various enzyme reactions constituting the network. Among these properties are adaptability and homeostasis, but also multiple steady