Enzymes and Coenzymes
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What is the definition of an enzyme?
A biological catalyst which speeds up the rate of a reaction without altering the final equilibrium between reactants and products.
Enzymes will usually catalyse only — type of reaction.
One
What are the 6 groups in which enzymes can be specified into due to the reaction they cataylse?
• Transfer of functional groups from donors to acceptors • Transfer of hydrogen atoms and electrons (oxidation and reduction) • Formation of double bonds or addition of groups to the double bond • Cleavage of bonds by addition of water (hydrolysis) • Transfer of functional groups within the same molecule • ATP to catalyse the formation of new covalent bonds
What does the active site of enzymes contain?
Functional groups to stabilise the transition state of a reaction
What bonds stabilise enzyme structure?
H - bonds Electrostatic forces Hydrophobic interactions
How does a kinase enzyme change the substrate so it fits better in the active site?
It phosphorylates the substrate which distorts it and allows it to then bind to the active site.
In the enzyme example of catalysis of peptide bond by chymotrypsin, what are the 3 amino acids in the active site and how are they arranged?
Serine, histadine and aspitate. Must be in this order so that the active site is positioned so that the histadine is in the middle between the nucleophile and the acid.
What is bonded so that the histadine sits in the middle of the amino acids in the active side?
Hydrogen atom on a hydroxyl group of serine bind to a nitrogen on histadine Amine group on histadine is attached to the carbonyl group of aspartic acid.
Explain what isoenzymes are
Enzymes with different protein structures which have been transcribed from the same genes with different protein structures which catalyse the same reaction
How many monomers does lactate dehydrogenase have?
4 monomers They catalyse the same reaction with a different isomer