perature fluctuations in their surroundings and
must, therefore, possess compensatory biochemical mechanisms. The stabilization of membrane
viscosity through the "homeoviscous" regulation
of the lipid composition should be mentioned
here (p.598), but most important of all is the
temperature compensation of enzyme activity. As
the substrate affinity of an enzyme declines with
increasing temperature (i.e. the Km increases) but
at the same time kcat and V max increase, the quotient kcatlKm' which is an approximate measure of
the in vivo catalytic activity, will be temperature
independent and constant [3, 15, 31]. Many poikilothermal organisms possess isoenzymes with
differing temperature optima, and the proportions of these can be variably adjusted. Specific
adaptations to low temperature may be found in
many animals, whilst heat-resistant animal species, comparable to the thermophilic bacteria, are
unknown [11, 15]. Particularly interesting from a
comparative biochemistry point of view are the
various cryoprotective substances of animals:
these include the accumulation of glycerol and
sorbitol in many insects (p.466) and, above all,
the independent occurrence of cryoprotective
proteins in arctic and antarctic fish and in several
terrestrial arthropods (p. 207).
An especially enticing theme is the biochemical adaptations of deep-sea animals, which withstand hydrostatic pressures of up to 1160 bar
[13, 18,26]. Many pressure experiments on enzymes produce only indications of the stability of
protein structures [21]. In 1973, however, a special expedition was mounted to research the
biochemical-ecological problems of deep-sea
creatures [14]. All effects of pressure are related
to volume changes: if a chemical process is
accompanied by an increase in volume, it will be
negatively affected by increased pressure but promoted by a fall in pressure. Volume changes in
proteins arise more from alterations in the state
of hydration than from alterations in conformation. The association of protein subunits results in
the release of water at the contact points and,
thus, in an increase in volume; pressure, therefore, promotes the dissociation of oligomeric
enzymes. The evolution of deep-sea animals,
however, does not go in the direction of preference for monomeric enzymes, as was believed for
a time, but rather towards a strengthening of nonpolar interactions between the subunits. Ligand
binding and the catalytic activity of enzymes are
also accompanied by volume changes, and are
thus pressure dependent and the subject of adaptive evolutionary processes. Membrane structure
References
7
is also pressure dependent but the corresponding
adaptive changes in membrane lipids have, as yet,
been little investigated.
References
1. Baldwin E.: An introduction to comparative biochemistry, 4. ed. Cambridge Univ. Press, Cambridge 1964
2. Brachet J., Alexandre H.: Introduction to molecular
embryology, 2. ed. Springer, Berlin 1986
3. Crockett E.L. and Sidell, B.D.: Some pathways of
energy metabolism are cold adapted in Antarctic
fishes. Physio!. Zoo!. 63: 472-488 (1990)
4. Dayhoff M. 0.: Atlas of protein sequences and structure, Vo!. 5 and Supp!. 1-3. Nat. Biomed. Res.
Foundation, Washington 1972-78
5. DiPrisco G.: Life under extreme conditionsBiochemical adaptation. Springer, Berlin 1991
6. Dixon M. and Webb E. C.: Enzymes. Longmans, London 1958
7. Engelmann W: Biorhythmen. Quelle & Meyer, Heidelberg 1983
8. Evered D. and Collins G. M. (eds.): Origins and
development of adaptations. Pitman, London 1984
9. von Ftihrt 0.: Vergleichende chemische Physiologie
der niederen TIere. G. Fischer, Jena 1903
10. Goto Y. et a!.: Heterogeneity in the liver mitochondria
of the tadpole, Rana catesbeiana. Compo Biochem.
Physio!. Pt. B 72: 637-640 (1982)
11. Grout B. W Wand Morris G. J. (eds.): The effect of
low temperature on biological systems. E. Arnold,
London 1984
12. Haeussinger, D.: Nitrogen metabolism in liver: structural and functional organisation and physiological relevance. Biochem. J. 267: 281-290 (1990)
13. Henessy J. P. jr. and Siebenaller J. E: Inactivation of
NAD-dependent dehydrogenases from shallow- and
deep-living fishes by hydrostatic pressure and proteolysis. Biochim. biophys. Acta 913: 285-291 (1987)
14. Hochachka P. W: Biochemistry at depth. Compo Biochern. Physio!. Pt B 52: 1-199 (1975)
15. Hochachka P.W. and Somero G.N.: Biochemical
adaptation. Princeton Univ. Press, Princeton 1984
16. Hoffmann K. H.: Environmental physiology and biochemistry of insects. Springer, Berlin 1984
17. International Union of Biochemistry: Enzyme
nomenclature 1984. Acad. Press, New York 1984
18. Jaenicke R.: Biochemical processes under high hydrostatic pressure. Naturwissenschaften 70: 332-341 (1983)
19. Kerkut G. A.: Which insects are most used in physiological and biochemical research? Compo Biochem.
Physio!. Pt. A 81: 705-706 (1985)
20. Kerkut G. A. and Gilbert L. I. (eds.): Comprehensive
insect physiology, biochemistry and pharmacology. 13
vo!. set. Pergamon Press, Oxford 1985
21. Kornblatt M. J. and Hoa G. H. B.: The pressureinduced inactivation of mammalian enolases is accompanied by dissociation of the dimeric enzyme. Arch.
Biochem. Biophys. 252: 277-283 (1987)
22. Krebs H. A.: The August Krogh principle: "For many
problems there is an animal on which it can be most
conveniently studied". J. expo Zoo!. 194: 221-226
(1975)
must, therefore, possess compensatory biochemical mechanisms. The stabilization of membrane
viscosity through the "homeoviscous" regulation
of the lipid composition should be mentioned
here (p.598), but most important of all is the
temperature compensation of enzyme activity. As
the substrate affinity of an enzyme declines with
increasing temperature (i.e. the Km increases) but
at the same time kcat and V max increase, the quotient kcatlKm' which is an approximate measure of
the in vivo catalytic activity, will be temperature
independent and constant [3, 15, 31]. Many poikilothermal organisms possess isoenzymes with
differing temperature optima, and the proportions of these can be variably adjusted. Specific
adaptations to low temperature may be found in
many animals, whilst heat-resistant animal species, comparable to the thermophilic bacteria, are
unknown [11, 15]. Particularly interesting from a
comparative biochemistry point of view are the
various cryoprotective substances of animals:
these include the accumulation of glycerol and
sorbitol in many insects (p.466) and, above all,
the independent occurrence of cryoprotective
proteins in arctic and antarctic fish and in several
terrestrial arthropods (p. 207).
An especially enticing theme is the biochemical adaptations of deep-sea animals, which withstand hydrostatic pressures of up to 1160 bar
[13, 18,26]. Many pressure experiments on enzymes produce only indications of the stability of
protein structures [21]. In 1973, however, a special expedition was mounted to research the
biochemical-ecological problems of deep-sea
creatures [14]. All effects of pressure are related
to volume changes: if a chemical process is
accompanied by an increase in volume, it will be
negatively affected by increased pressure but promoted by a fall in pressure. Volume changes in
proteins arise more from alterations in the state
of hydration than from alterations in conformation. The association of protein subunits results in
the release of water at the contact points and,
thus, in an increase in volume; pressure, therefore, promotes the dissociation of oligomeric
enzymes. The evolution of deep-sea animals,
however, does not go in the direction of preference for monomeric enzymes, as was believed for
a time, but rather towards a strengthening of nonpolar interactions between the subunits. Ligand
binding and the catalytic activity of enzymes are
also accompanied by volume changes, and are
thus pressure dependent and the subject of adaptive evolutionary processes. Membrane structure
References
7
is also pressure dependent but the corresponding
adaptive changes in membrane lipids have, as yet,
been little investigated.
References
1. Baldwin E.: An introduction to comparative biochemistry, 4. ed. Cambridge Univ. Press, Cambridge 1964
2. Brachet J., Alexandre H.: Introduction to molecular
embryology, 2. ed. Springer, Berlin 1986
3. Crockett E.L. and Sidell, B.D.: Some pathways of
energy metabolism are cold adapted in Antarctic
fishes. Physio!. Zoo!. 63: 472-488 (1990)
4. Dayhoff M. 0.: Atlas of protein sequences and structure, Vo!. 5 and Supp!. 1-3. Nat. Biomed. Res.
Foundation, Washington 1972-78
5. DiPrisco G.: Life under extreme conditionsBiochemical adaptation. Springer, Berlin 1991
6. Dixon M. and Webb E. C.: Enzymes. Longmans, London 1958
7. Engelmann W: Biorhythmen. Quelle & Meyer, Heidelberg 1983
8. Evered D. and Collins G. M. (eds.): Origins and
development of adaptations. Pitman, London 1984
9. von Ftihrt 0.: Vergleichende chemische Physiologie
der niederen TIere. G. Fischer, Jena 1903
10. Goto Y. et a!.: Heterogeneity in the liver mitochondria
of the tadpole, Rana catesbeiana. Compo Biochem.
Physio!. Pt. B 72: 637-640 (1982)
11. Grout B. W Wand Morris G. J. (eds.): The effect of
low temperature on biological systems. E. Arnold,
London 1984
12. Haeussinger, D.: Nitrogen metabolism in liver: structural and functional organisation and physiological relevance. Biochem. J. 267: 281-290 (1990)
13. Henessy J. P. jr. and Siebenaller J. E: Inactivation of
NAD-dependent dehydrogenases from shallow- and
deep-living fishes by hydrostatic pressure and proteolysis. Biochim. biophys. Acta 913: 285-291 (1987)
14. Hochachka P. W: Biochemistry at depth. Compo Biochern. Physio!. Pt B 52: 1-199 (1975)
15. Hochachka P.W. and Somero G.N.: Biochemical
adaptation. Princeton Univ. Press, Princeton 1984
16. Hoffmann K. H.: Environmental physiology and biochemistry of insects. Springer, Berlin 1984
17. International Union of Biochemistry: Enzyme
nomenclature 1984. Acad. Press, New York 1984
18. Jaenicke R.: Biochemical processes under high hydrostatic pressure. Naturwissenschaften 70: 332-341 (1983)
19. Kerkut G. A.: Which insects are most used in physiological and biochemical research? Compo Biochem.
Physio!. Pt. A 81: 705-706 (1985)
20. Kerkut G. A. and Gilbert L. I. (eds.): Comprehensive
insect physiology, biochemistry and pharmacology. 13
vo!. set. Pergamon Press, Oxford 1985
21. Kornblatt M. J. and Hoa G. H. B.: The pressureinduced inactivation of mammalian enolases is accompanied by dissociation of the dimeric enzyme. Arch.
Biochem. Biophys. 252: 277-283 (1987)
22. Krebs H. A.: The August Krogh principle: "For many
problems there is an animal on which it can be most
conveniently studied". J. expo Zoo!. 194: 221-226
(1975)