Biosynthesis of Aromatic Compounds. Proceedings of the 2nd Meeting of the Federation of European Biochemical Societies, Vienna, 21–24 April 1965

139 Pages·1966·3.85 MB·English

by  G. Billek (Eds.)

FEDERATION OF EUROPEAN BIOCHEMICAL
SOCIETIES (FEBS)
A Federation of Biochemical Societies in the European Area representing
Societies in Austria, Belgium, Bulgaria, Czechoslovakia, Denmark, Finland,
France, Germany, Great Britain, Hungary, Israel, Italy, The Netherlands,
Norway, Poland, Portugal, Spain, Sweden, Switzerland, Yugoslavia.
OFFICERS (1965):
Chairman: O. Hoifmann-Ostenhof
Secretary: G. Billek
Treasurer: K. H. Spitzy
Council: E. Auhagen, P. Cerletti, J. E. Courtois, S. P. Gomes da Costa,
J. Hofejsi, C. Liebecq, U. Littauer, F. Lundquist, P. Mildner, Τ. Nikolov,
A. Pihl, T. Posternak, S. Rappoport, P. Reichard, J. J. Saukkonen, A. Sols,
B. Tankσ, Η. Veldstra, W. J. Whelan, K. Zakrzewski.
Proceedings of the 2nd Meeting of the Federation of
European Biochemical Societies, Vienna, 21-24 April 1965
Volume 3
Colloquium
BIOSYNTHESIS OF
AROMATIC COMPOUNDS
Edited by
G. BILLEK
Unilever Research Laboratory Hamburg,
Hamburg, Germany
SYMPOSIUM PUBLICATIONS DIVISION
PERGAMON PRESS
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Copyright © 1966
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First edition 1966
Library of Congress Catalog Card No. 65-28548
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LIST OF CONTRIBUTORS
R. AzERAD, Institut de Biochimie, Facultι des Sciences de l'Universitι de
Paris, Orsay (S. & O.), France.
W. BARZ, Institut fόr Biochemie der Pflanzen der Universitδt Freiburg,
Freiburg i.Br., Germany.
Α. R. BATTERSBY, University of Liverpool, The Robert Robinson Labora­
tories, Liverpool 17, England.
G. BILLEK, Organisch-chemisches Institut der Universitδt Wien, Wien 9,
Austria.
Present address: Unilever Forschungslaboratorium Hamburg, Hamburg
50, Germany.
Α. J. BIRCH, University of Manchester, Manchester 13, England.
E. F. BLEICHERT, Department of Biology, Dalhousie University, Halifax,
Nova Scotia, Canada.
Present address: Botany Department, Cornell University, Ithaca,
New York, USA.
R. BLEILER-HILL, Institut de Biochimie, Facultι des Sciences de l'Universitι
de Paris, Orsay (S. & O.), France.
S. A. BROW^N, Trent University, Peterborough, Ontario, Canada.
Η. GRISEBACH, Institut fόr Biochemie der Pflanzen der Universitδt Freiburg,
Freiburg i.Br., Germany.
Κ. HAHLBROCK, Institut fόr Biochemie der Pflanzen der Universitδt Freiburg,
Freiburg i.Br., Germany.
S. KELLNER, Institut fόr Biochemie der Pflanzen der Universitδt Freiburg,
Freiburg i.Br., Germany.
Κ. KRATZL, Organisch-chemisches Institut der Universitδt Wien, Wien 9,
Austria.
Ε. LEDERER, Institut de Biochimie, Facultι des Sciences de l'Universitι de
Paris, Orsay (S. & O.), France.
K. MOTHES, Deutsche Akademie der Wissenschaften zu Berlin, Institut fόr
Biochemie der Pflanzen, Halle a.d. Saale, Germany.
Α. C. NEISH, Atlantic Regional Laboratory, National Research Council,
Halifax, Nova Scotia, Canada.
J. ΟκΑΒΕ, Organisch-chemisches Institut der Universitδt Wien, Wien 9,
Austria.
Present address: Sanyo Pulp Co. Ltd., Iwakuni, Japan.
L. PATSCHKE, Institut fόr Biochemie der Pflanzen der Universitδt Freiburg,
Freiburg i.Br., Germany.
vii
VIH LIST OF CONTRIBUTORS
C. RATLEDGE, Medical Research Council of Ireland, Trinity College,
Dubhn 2, Ireland.
Present address: Unilever Research Laboratory Colworth House,
Sharnbrook, Bedford, England.
A. ScHiMPL, Organisch-chemisches Institut der Universitδt Wien, Wien 9,
Austria.
Present address: Institut de Biochimie, Facultι des Sciences de
rUniversitι de Paris, Orsay (S. & O.), France.
K. SCHUBERT, Deutsche Akademie der Wissenschaften zu Berlin, Institut
fόr Mikrobiologie und experimentelle Therapie, Abteilung fόr Steroid-
forschung, Jena, Germany.
G. H. N. TOWERS, Atlantic Regional Laboratory, National Research Council,
Halifax, Nova Scotia, Canada.
Present address: Department of Botany, University of British Columbia,
Vancouver 8, British Columbia, Canada.
E. W. UNDERHILL, Prairie Regional Laboratory, National Research Council,
Saskatoon, Saskatchewan, Canada.
L. R. WETTER, Prairie Regional Laboratory, National Research Council,
Saskatoon, Saskatchewan, Canada.
M. H. ZENK, Botanisches Institut der Universitδt Mόnchen, Mόnchen 19,
Germany.
PREFACE
THE 2nd Meeting of the Federation of European Biochemical Societies,
organized by the "Österreichische Biochemische Gesellschaft", was held at
the University of Vienna from 21 to 24 April, 1965. The organization com
mittee decided to include into the programme of this meeting, among others,
a colloquium on "Biosynthesis of Aromatic Compounds". The main papers
were delivered by invited speakers. Additionally, however, a limited number
of papers on the subjects of this colloquium have been accepted. The contri
butions to this colloquium were selected in an endeavour to cover most of
the current investigations on the biosynthesis of aromatic compounds.
This volume is based on the lectures which were given at the colloquium
held during the above-mentioned meeting in Vienna. Though it was not
possible at a meeting of this type to provide a comprehensive coverage of the
subject, the authors have been asked to give not only a record of their
papers but also to expand their contributions and to add references to prior
and related investigations.
The main pathways involved in the biosynthesis of aromatic compounds
are now well known and the formation of these compounds seems to be
closely linked to the general metabolism of plant tissue. Modern methods,
and in particular the use of radioactive tracers, have shown that acetate
units as well as compounds derived from carbohydrate metabolism, like
shikimic, chorismic and prephenic acid, may act as precursors of aromatic
rings. Besides experimental work, some ideas based on a method which may
be called comparative anatomy cf the structure of plant constituents gave
new impetus in clarifying the formation cf rather odd shaped compounds.
On the contrary, one must not overlook that identical structures may have
entirely biogenetic origin, even in species of the same family.
The opening lecture, by Professor A. J. Birch and given in the first chapter
of this book, was concerned with plant constituents derived from acetate
pathways. Chapter 2 deals with the biosynthesis of coumarins which, on
the other hand, are formed exclusively from derivatives of carbohydrate
metabolism. Other compounds like ñavonoids and stilbenes originate
from the interaction of both pathways. New results in these fields are reported
in the following two chapters. Recent investigations on the biosynthesis of
benzoic acids showed that many of these compounds, especially in higher
plants, are formed by degradation of the corresponding cinnamic acids. In
Chapter 5 Dr. M. H. Zenk gives an up-to-date report on this problem
extending his own work to related compounds like substituted benzaldehydes
ix
χ PREFACE
and benzylalcohols. The conversion of cinnamic acids to C^-Ci compounds
seems to be widespread in higher plants only. Besides this a direct conversion
of shikimic acid into compounds of the C^-Ci type has been found many
times, especially in lower plants and microorganisms. Additional observations
are given in Chapter 6. The last three chapters of Part I deal with entirely
different problems which, however, are in close connection with the topics of
the colloquium; incorporation of /7-hydroxybenzoic acid into lignins, the
introduction of a methyl group into the aromatic ring of a certain vitamin
K, and finally the aromatization of steroids in microbial metabolism.
The second part of this book is devoted to investigations on the bio­
synthesis of aromatic compounds containing hetero atoms. Among these,
without any doubt, the formation of alkaloids is still a fascinating problem.
Professor Dr. K. Mothes and Professor A. R. Battersby discuss various
aspects on the biosynthesis of alkaloids. Carefully selected examples of
thoroughly investigated pathways underline the subject's complexity.These
lectures are covered by Chapters 10 and 11. Investigations on the formation
of taxiphyllin (Chapter 12) and recent work on mustard oil glucosides
(Chapter 13) were reported by Canadian scientists who were not deterred by
the long distance to Vienna.
Special thanks are due to authors of papers for their co-operation and to
the Symposium Publications Division of Pergamon Press for the preparation
of this book.
Hamburg, 1965 G. BILLEK
CHAPTER 1
BIOSYNTHETIC INTERMEDIATES
IN POLYKETIDE BIOSYNTHESIS
A. J. BIRCH
University of Manchester
Two related main themes run through this discussion: one concerns the
number of biochemical problems which the organic chemist has raised but
incompletely solved, the other is the contribution made by organic mechanism
theory in understanding biochemical reactions. The subject of polyketide
biosynthesis was, for example, an extrapolation, on grounds of mechanisms
of cyclization, from biochemical discoveries in connection with the bio­
synthesis of fatty acids. The polyketide theory then in turn has raised a number
of problems, for example of intermediates, which only the biochemist can
solve, using biochemical experimental techniques. A number of similar
examples of interaction of the organic and biochemist could be cited, includ­
ing the important subject of phenol oxidation (e.g. Scott, 1965).
The organic approach is probably most fruitful in connection with re­
latively complicated molecules of types which have only recently been
examined by the classical biochemist. These are frequently of the class
labelled "secondary metabolite" often of unknown or ill-defined function,
but including for convenience any substance in which the chemist is interested.
The polyketides, produced mainly by fungi and to a lesser extent by higher
plants, often have no obvious function, but include a number of antibiotic
substances and plant pigments. The chief characteristic is a random and
restricted distribution in different organisms.
For convenience, the process of biosynthesis of such a substance can be
divided arbitrarily into stages:
(i) Correctly activated small molecules are produced in normal metabolic
processes connected with structural components or energy-release. With
polyketides the coenzyme-A esters of acids, particularly acetic and malonic
acids, are involved.
(ii) These units are linked to produce skeletons distinct from those of
normal metabolic intermediates. At this stage derivatives of stable molecules
may be formed, or the products may be enzyme-bound complexes.
(iii) These intermediates are converted into isolable stable compounds, for
example by removal of coenzymes (e.g. removal of coenzyme-A from esters),
3
4 Α. J. BIRCH
by further hnkage with other activated molecules, or by aromatization or
oxidation-reduction reactions.
(iv) The products of such processes are often metabolized further in a
completely distinct stage, usually as the result of oxidation apparently on the
way to complete oxidated breakdown. An example is the conversion of
6-methylsalicylic acid into patulin. It is evident that these stages are not
sharply divisible by definition.
The fundamental interest lies in the processes rather than in the final
product which is an expression of them. Identical molecules, for example
nicotinic acid, may in different cases be the expression of different processes
and are therefore different from a number of viewpoints, including phylogeny
(Birch, 1964).
Let us consider some polyketides, taking that term to include compounds
derived wholly or in part by the acetyl-malonyl coenzyme-A route, and having
^-polyketo-acid intermediates. The original postulation of the route (Birch
and Donovan, 1953)* was based on a consideration of mechanistically
acceptable cyclizations of hypothetical coenzyme-A esters of jS-polyketo-acid
chains still containing the carbonyl groups as remnants of their origin from
active "acetate" units. The reactions involved cyclizations by aldol-condensa-
tion (II) or Claisen-condensation (VI), of chains, now known to be generated
as in (I). In view of the original idea it is not surprising that the subject
continues to remain in line with fatty acid biosynthesis, the original chain-
building unit (acetyl coenzyme-A) (Birch and Donovan, 1953) being replaced
by the more recently discovered malonyl coenzyme-A (e.g. Bu'Lock and
Smalley, 1961; Birch, Cassera and Rickards, 1961).
Many of the details of reactions such as those below can only be defined by
biochemical work. For example, HSR could be coenzyme-A, or the deriv­
atives could be transferred to HS-groups on an assembling enzyme. From
structural and other considerations it has always seemed likely that assembly
starts from the acetyl (or other acyl) coenzyme-A unit. From (II) the aldol
product (IV) should be reasonably stable, but probably convertible reversibly
back into the original chain, or irreversibly by dehydration into an aromatic
compound. The latter process need not be, and probably would not be,
spontaneous, but enzyme-catalysed. By the alternative scheme, (VI) should
give (VII) (or an enol thereof) which is much less likely to be reversible into
(VI) and might well aromatize spontaneously. This has consequences in
*An earlier theory of Collie (1907) on the origin of orsellinic acid is superficially similar,
but did not involve chains in the same way. He suggested that orsellinic acid (V) arises from
two molecules of acetoacetic acid (III) and implied a more general application, although
he did not discuss examples. If credited with this theory he should also be credited with the
first suggestion that terpenes and fatty acids arise from acetic acid. Most of his work was
connected with the erroneous derivation of carbohydrates by a mechanically unacceptable
hydration of enols of ß-polyketones. Robinson (1955) apparently developed Collie's theory
into a similar one to our own, but published it for the first time in 1955.
BIOSYNTHETIC INTERMEDIATES IN POLYKETIDE BIOSYNTHESIS 5
connection with other reactions—reduction of a carbonyl could, for example,
occur in either (Π) or (IV), it is unlikely to occur in (VII) and removal of an
oxygen from the ring due to this cause is likely to be due to reaction at the
open-chain stage in the case of compounds produced by Claisen-condensation.
The enolic forms written below are not intended to show stable forms, but
rather to indicate the requirements of reactivity as understood by the organic
chemist.
H-^H/C02© (OH 0
MeC M0eC CH2COSR- -Me C CH2COSR—etc.
SR COSR ""SR
I
•COSR
FIG.
The required configurations and conformations of the chains are different,
and different enolic forms are required, in order to produce alternative ring-
closures. The major, and still unsettled, problem is the form in which the
polyketo-ester molecules are assembled and exist before the first stable
(usually aromatic) intermediate is released. There is, however, good evidence
that the initial chain can in some cases undergo alternative ring-closures