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Allosteric Regulatory Enzymes
Edited by Thomas Traut
Springer
2008
Hardcover 250 pp ISBN 9780387728889
£99.00
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All enzymes are remarkable since they have the ability to increase the rate of a chemical reaction,
often by more than a billion-fold. Allosteric enzymes are even more amazing because the have
the additional ability to change their rate in response to cellular activators or inhibitors. This enables
them to control the pathway in which they are the regulatory enzyme. Since the effector molecules
represent the current status of the cell for a given metabolic pathway, this results in very responsive
and balanced metabolic states, and makes it possible for cells and organisms to be appropriately
dynamic, and responsive, in a changing environment. This book provides a logical introduction to the limits
for enzyme function as dictated by the factors that are limits for life. This book presents a complete description
of all the mechanisms used for changing enzyme acticity. Eight enzymes are used as model systems after extensive
study of their mechanisms. Wherever possible, the human form of the enzyme is used to illustrate the
regulatory features.
While authors often emphasize the few enzymes that have the most remarkable catalytic
rates, this survery of enzymes has led to the author's appreciation of some important, general
conclusions:
- Most enzymes are not exceptionally fast; they are always good enough for their specific catalytic step.
- Although enzymes could always be much faster if they changed so as to bind their substrates more weakly,
actual enzymes must be able to discriminate in favor of their special substrate, and therefore they have sacrificed
speed to obtain better binding. This means that specific control of individual metabolic steps is more important
than overall speed.
- Results for many hundreds of enzymes establish that a lower limit for a normal catalytic activity is
1 s-1. Most enzymes have a catalytic rate between 10 and 300 s-1.
- Allosteric regulation always results in a chance in the enzymes's affinity for its substrate.
Even V-type enzymes (named for their large chance in catalytic velocity) always have a corresponding
change in affinity for their substrate.
Written for biochemists, molecular biologists, cell biologists, chemists, biophysicists.
Contents
SECTION I OVERVIEW OF ENZYMES
- Introduction To Enzymes
- The Limits For Life Define The Limits For Enzymes
- Enzyme Kinetics
- Properties And Evolution Of Allosteric Enzymes
- Kinetics Of Allosteric Enzymes
SECTION II K-TYPE ENZYMES
- Hemoglobin
- Phosphofructokinase
- Glycogen Phosphorylase
- Ribonucleotide Reductase
- Hexokinase
SECTION III V-TYPE ENZYMES
- Introduction To V-Type Enzymes
- Protein Kinases
- G Proteins
References
Index
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