Enzymes. Enzymes : Biological catalysts that promote and speed up chemical reactions without themselves being altered (consumed) in the process. They determine the patterns of transformations for chemicals, as well as forms of energy in the living organisms.
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Enzymes: Biological catalysts that promote and speed up chemical reactions without themselves being altered (consumed) in the process.
They determine the patterns of transformations for chemicals, as well as forms of energy in the living organisms.
Before it was known that enzymes are proteins!!!
The rate is proportional to the
concentration of the reactant
in a typical chemical reaction.
Enzymes however showed
a saturation kinetics:
formation of ES complex
was hypothesized (1902).
Northrop, J. H. (1930)
“Crystallin pepsin, 1:
Isolation and tests of
purity” J. Gen . Physiol.
Not all enzymes are proteins: Some RNA molecules (ribozymes) were found to be catalytic (Sidney Altman and Thomas Cech, 1989).Ribozymes are found to promote RNA processing.
Sidney Altman visiting PKU
2 H2O2→ 2 H2O + O2
Fe3+ →1000 fold
Hemoglobin → 1 ,000,000 fold
Catalase → 1 ,000,000,000 fold
200,000 catalytic events/second/subunit
(near the diffusion-controlled limit).
The reaction is sped up by a billion fold!
(a prosthetic group)
Be often regulated.
-First part is the name of the substrates for the enzyme.
-Second part is the type of reaction catalyzed by the enzyme.This part ends with the suffix “ase”.
Example: Lactate dehydrogenase
Enzymes are classified into six different groups according to the reaction being catalyzed. The nomenclature was determined by the Enzyme Commission in 1961 (with the latest update having occurred in 1992), hence all enzymes are assigned an “EC” number. The classification does not take into account amino acid sequence (ie, homology), protein structure, or chemical mechanism.