Bke2 Biochemistry Lectures

Lecture 11: Intoduction to enzymes
Reading material: Horton, chapters 6 (Stryer, ch 8)

Abstract: Enzymes are macromolecules, usually proteins, that can catalyse (speed up) particular chemical reactions. They usually do so by binding the needed reactants (substrates) in an active site that is precisely suited to the chemistry to be carried out. Active sites contain amino acid side-chains or bound cofactors that can act as nucleophiles, proton abstractors, proton donors etc. For example, in serine proteases a serine acts as a nucleophile and a histidine acts as a proton abstractor/donor. The enzymatic reactions often take place in the hydrophobic environment of the active site where the effect of charges is increased and water is excluded. Enzymes speed up chemical reactions by bringing together reacting groups ("proximity effect"), by stabilizing the transition state of the reaction so that the activation energy is lowered, and by provding specific chemical groups for acid/base or covalent catalysis.

Key concepts:
Enzyme catalysis
Active sites provide a highly specialised reaction vessel
Specificity
Substrate, intermediate, transition state, product
Transition state stabilisation
Proximity effect ("Närhetseffekten")
Acid/base catalysis
Covalent catalysis
Cofactors

Links:
The MIT hypertext book: Enzymes
A chapter on the Properties of Enzymes from the text book "Principles of Biochemistry" (Horton, Moran, Ochs, Rawn and Scrimgeour; 2nd edition, Prentice Hall 1996) is available on-line.
Databases with information about enzymes are available on-line. Find out more in BioTech's Introduction to Enzyme Databases

Lecture index

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