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Book Review Molybdenum Enzymes. Edited by T. G. Spiro

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cule in the gas phase is first discussed (Ion Solvation in the
Gas Phase). This is followed by a treatment of the solvation of a single ion by many solvent molecules, as in a dilute solution, dealing with structural, spectrochemical, and
kinetic aspects. Chapter 3 (Interaction Models for Ion Solvation) describes various theoretical models based on statistical thermodynamics considerations. Chapter 4 (Structural and Kinetic Aspects) deals with changes in the dynamic behavior of the solvent molecules caused by ion solvation. Concepts such as first and second solvation shells,
primary and secondary solvation, and coordination and
solvation numbers, are here put into an up-to-date context.
Chapter 5 (Ion Hydration) deals with the special position
occupied by water as a solvent for electrolytes, being concerned exclusively with the thermodynamic and structural
aspects of the ion/water interaction. The growing importance of ions in nonaqueous organic solvents is recognised
in the following chapter (Ion Solvation in Nonaqueous
Solvents). Detailed tables listing relevant properties of
nonaqueous solvents (including empirical parameters of
solvent polarity), and of Gibbs transfer energies AG: (X,
H,O-S)/kJ.mol- ’) for single ions, make this chapter one
of the most useful in the book. Here the reader benefits
from the knowledge which the author gathered in compiling (for IUPAC) critical tables of Gibbs transfer energies,
enthalpies, and entropies for the transfer of single ions
from water into nonaqueous solvents [ Y . Marcus, Pure d
Appl. Chem. 55 (1983) 977; ibid. 57 (1985) 11031. Attempts
at correlating such Gibbs transfer energies with intrinsic
solvent properties using multiparameter equations are also
described.
Chapter 7 is devoted to the selective solvation of ions in
binary solvent mixtures. Chapter 8 deals with solvation of
ion pairs, with particular attention to molten hydrated
salts, perhaps as a result of the author’s laboratory being
near the Dead Sea (Dead Sea Water contains a 8.8 mol
ions/liter!). In the final chapter (Some Applications of Ion
Solvation) many different applications in the fields of electrochemistry, hydrometallurgy, solvent extraction, and organic synthesis are discussed.
The book excels in having a lucid, readable style, and
the detailed author and subject indexes make it easy to
use. Lists of references at the end of each chapter (more
than 310 references altogether) enable the reader to gain
easy access to original papers-although that should often
be unnecessary, since the 64 tables and 36 figures provide
a wealth of useful information. The book should be included in every library, and anyone who can afford to (at
the price of DM 175.00!) should have the book on his
desk-he will certainly get a lot of use from it.
Christian Reichardt [NB 813 IE]
Fachbereich Chemie
der Universitat Marburg (FRG)
Molybdenum Enzymes. Edited by T. C . Spiro. Wiley, ChiChester, England 1985. x, 61 I pp., hardcover, $ 125.00.ISBN 0-47 1-88542-8
This book collects some excellent reviews on the inorganic chemistry and biochemistry of molybdenum, molybdenum-containing enzymes, and the molybdenum-containing cofactors. As noted by P. J. Stephens in his chapter, the
general area of molybdenum enzymes, especially as related
to nitrogen fixation, has been extensively reviewed in comparison to research productivity. These reviews are, however, a significant new contribution because of the emphaAnyen..
(%mi
in!. Ed. Engl. 26 11987) N i l . 5
sis on the chemical aspects as opposed to the agricultural
and genetic aspects. The authors are well chosen, critical,
and careful to avoid oversimplification or overinterpretation. The literature is completely covered through 1983
with some references to 1984. The ten chapters overlap
some in their scope; thus, there is some redundancy that
would not occur in a monograph by a single author. However, to carry on the editor’s analogy, although some of the
same territory is being explored, it is being seen through
different eyes and to different purposes.
Chapter 1, by R. H . Holm and E. Simhon, is a thorough
survey of molybdenum- and tungsten-containing iron-sulfur clusters, their structure, physical properties, reactivity,
especially with respect to substitution and electrochemistry, and synthesis. These results are then discussed by comparison to the properties of the iron-molybdenum cofactor
from nitrogenase. The second chapter, by E . Stiefel and S .
Cramer, concerns the isolation, composition, physical and
chemical properties, assay, and biosynthesis of the ironmolybdenum cofactor. The same authors discuss the molybdenum cofactor (the molybdenum center of enzymes
other than nitrogenase) in Chapter 8.
Chapter 3, by P. J. Stephens, reviews structures of the
iron and iron-molybdenum proteins that compose the nitrogenase enzyme. This review is organized by presenting
the “Dominant Hypothesis” concerning each protein, and
then presenting the experimental data. Conflicts between
the “Dominant Hypothesis” and the data are pointed out
in a stimulating presentation. For example, there are problems with the hypotheses about the types and number of
clusters in light of the cysteine analysis of the proteins.
The next two chapters concern the reactions of nitrogenase. B. Burgess presents a discussion of the varied substrates of nitrogenase and describes the steady-state kinetics results. Emphasis is put on the importance of considering electron flow through the enzyme, careful product
analysis, and the problems of controlling the “inputs” to
the enzyme (reducing equivalents, MgATP, substrate, medium). There is also some discussion of substrate interaction, the evidence for interacting sites on the enzyme, and
the problem of the competition between hydrogen evolution and substrate reduction.
Chapter 5 , by R. 7’horneley and D. Lowe, is the most detailed discussion of the mechanism of nitrogenase. The authors attempt to fit a mechanism and individual rate constants particularly to the reactions of the Klebsiella pneumoniae proteins. The work especially involves the authors’
pre-steady-state kinetics measurements, but also encompasses the steady-state measurements. This type of detailed
analysis is necessary in order to get a real understanding of
this complex system, and in order to avoid errors from too
facile interpretation of individual experiments, but the details will appeal more to committed kineticists. The next
chapter, by M . Hidai, reviews the diverse work o n the inorganic and organometallic chemistry of complexes of dinitrogen and their reactivity. Unfortunately, there still remains little connection between these studies and advances
in the understanding of nitrogenase.
The remaining four chapters concern molybdenum-containing proteins other than nitrogenase. Chapter 7 by D.
Garner and S . Brisfow presents the inorganic background
through a discussion of oxomolybdenum chemistry. This
long presentation also demonstrates the relevance of the
measurements on the inorganic complexes to the study of
the enzymes. Chapter 8 o n the molybdenum cofactor is
next, followed by a detailed discussion by R. Hille and V.
Mussey primarily on xanthine oxidase. Here the emphasis
487
is properly on the molybdenum chemistry, but the flavin
chemistry is presented as necessary. A good discussion is
presented of the problem of the oxidation-reduction potentials of the centers and whether they are in equilibrium
with each other. The last chapter, by M . Adurns and L.
Mortenson, discusses nitrate reductase and formate dehydrogenase. Here, there is less physical information on the
proteins and the sites and more discussion on physiology,
purification, and characterization.
The book is well printed, with only a few errors in
layout, such as misplaced figures in Chapter 2 and some
missing compound numbers in Chapter 1. This is a solid
addition to any library for those interested in the chemistry
of molybdenum in biological systems and related inorganic chemistry.
Scot Wherlund [NB 790 IE]
Washington State University
Pullman, WA (USA)
Organized Multienzyme Systems: Catalytic Properties.
(Biotechnology and applied Biochemistry Series.)
Edited by G . R. Welch. Academic Press, New York 1985.
xiii, 458 pp., bound, $! 75.00.--ISBN 0-12-744040-2
This monograph summarizes, mainly from a biochemical and biological viewpoint, the extraordinary wealth of
information which exists o n organized multienzyme systems. In each of the nine chapters an expert in the relevant
topic outlines its most important features, with examples.
The topics discussed include the fundamentals of protein
organisation in mitochondria, catalytic processes and energy transfer in membranes, dynamic compartmentalization of multienzyme complexes in the cytoplasm, questions
concerning the flexibility and co-operativity of enzyme
molecules in the kinetics and regulatory mechanism of allosteric enzymes, and reversible adsorption as a modulator
of enzymatic activity. Mechanistic models for sequential
enzymatic pathways are also proposed and discussed, and
detailed analyses of the kinetics of multienzyme systems
are given. The monograph concludes with a chapter on
long-range energy continua, and their role in the transfer
and conservation of chemical energy in multienzyme sequences, and thus in the regulation of metabolism.
Chapters on naturally occurring multienzyme sequences
are especially appropriate to the aims of this monograph,
in showing the mode of action and structural features of
organized multienzyme systems and the role of the microenvironment, together with a critical discussion of current
theoretical models. On the other hand, Chapter 7, on the
kinetic analysis of multienzyme systems in homogeneous
solutions, falls outside the proper scope of the book. Kinetic models for sequential reactions, some of which are
already well-known, are laboriously presented here in a
complicated and unconventional notation. The inclusion
of a lengthy and not very useful 13-page digression into
the use of the Laplace-Carson transformation to solve ordinary differential equations is quite incomprehensible.
Apart from the availability of numerical computation
methods nowadays, there i s no obvious advantage in using
such laborious integral transformations rather than conventional integration methods. Furthermore, the literature
referred to is not always truly representative; for example
the book by Ayres (1952) on the theory of differentia! equations is now hardly the most appropriate source on the
trivial solution of the differential equations for a first-order reaction. However, readers who are engaged in theoretical work or interested in these aspects will be compensated by the discussion in Chapter 8 on the behaviour of
immobilized multienzyme systems, particularly in membranes. Here we find a successful combined presentation
of experimental studies of diffusion-limited enzymic reactions together with the relevant theoretical models, using
mathematical techniques of a practical nature which are
described in a comprehensible way. Especially noteworthy
is the elegant theoretical modelling of the highly nonlinear
diffusion-limited reaction effects in multienzyme systems
with complex control mechanisms. A reading of this chapter will also be of value to all process-oriented biotechnologists. Elsewhere in the monograph, however, there are
many places where, although it is assumed that the knowledge presented will be of interest to biotechnologists, no
relevant cross-reference is included. Consequently those
involved in the practice of biotechnology may have difficulty in making use of the abundant fundamental knowledge displayed. The one chapter whose title mentions
practical applications (Chapter 6- Models of organized
multienzyme systems: use in microenvironmental characterization and in practical application) is comparatively
vague, and deals with the practical aspects in a mere five
pages. The main emphasis is on coenzyme regeneration,
but the discussion of coupled equilibria does not, unfortunately, include the latest developments which have been
reported, e.g. for the enzyme membrane reactor.
The monograph thus demonstrates the importance and
the difficulties of communication in interdisciplinary fields
of knowledge. The book can be recommended to all who
are concerned with setting up immobilized cells for bioconversions, as the results, concepts and theoretical models presented here are of considerable importance for
them. Because of the comparatively high price, only highly
specialized readers and those with theoretical interests will
wish to buy it for their private libraries.
Maria-Regina Kulu [NB 788 IE]
Institut fur Enzymtechnologie
der Universit3t Diisseldorf
at KFA Julich GmbH (FRG)
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Angrw. Cliem. lnr. Ed. Engl. 26 119871 N o 5
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