文档介绍：Section C - Enzyme
C1C2 Introduction to Enzymes
C3 Enzyme ics
C4 Enzyme inhibition
C5 Regulation of Enzyme activity
C1C2 Introduction to Enzymes
Enzymes were among the first biological macromolecules to be studied chemically.
Much of the early history of biochemistry is the history of enzyme research.
Biological catalysts were first recognized in studying animal food digestion and sugar fermentation with yeast (brewing and wine making).
Ferments (., enzymes, meaning in “in yeast”) were thought (wrongly) to be inseparable from living yeast cells for quite some time (Louis Pasteur)
Yeast extracts were found to be able to ferment sugar to alcohol (Eduard Buchner, 1897, who won the Nobel Prize in Chemistry in 1907 for this discovery).
Enzymes were found to be proteins (1920s to 1930s, James Sumner on urease, “all enzymes are proteins”, John Northrop on pepsin, chymotrypsin and trypsin, both shared the 1946 Nobel Prize in Chemistry).
Almost every chemical reaction in a cell is catalyzed by an enzyme (thousands have been purified and studied, many more are still to be discovered!)
Proteins do not have the absolute monopoly on catalysis in cells. Catalytic RNA were found in the 1980s (Thomas Cech, Nobel Prize in Chemistry in 1989).
2. The most striking characteristics of enzymes are their immense catalytic power and high specificity.
Enzymes accelerate reactions by factors of at least a million.
Most reactions in biological systems do not occur at perceptible rates in the absence of enzymes.
The rate enhancements (rate with enzyme catalysis divided by rate without enzyme catalysis) brought about by enzymes are often in the range of 108 to 1020)
For carbonic anhydrase, an enzyme catalyzing the hydration of CO2 (H2O + CO2 HCO3- + H+), the rate enhancement is 107 (each enzyme molecule can hydrate 105 molecules of CO2 per second!)
Enzymes are highly specific both in the reaction catalyzed