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Lecture 4
Web: pollev.com/ucibio
Text: To: 37607Type in: 169964 <your
question>
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Enzymes and reactions
Spontaneity = ___
Enzyme = Decrease G# = _________________Mechanism = “Induced fit”
Rate = ___
“Active site” ________________ stabilize TS
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Decreasing DG‡: Proximity + Orientation
Active site:
Bring products togetherIn precise orientation
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Not just binding!
Forces change in substrate conformation as well!
Active site interactions can stabilize the TSActive site residues can initiate reactions
Keep molecules under “strain” to facilitate reaction
Different enzymes = Different mechanisms
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Glc Glc-6-P: Enzyme = Hexokinase
http://web.chem.ucsb.edu/~molvisual/ABLE/induced_fit/index.html
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Specificity of enzymes - Isomers
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Specificity of enzymes - Stereoisomers
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Effects of specificity – Tastes!
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Effects of specificity – Calories!
http://commons.wikimedia.org/wiki/File:D_et_l_glucose.png
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Effects of specificity – Treatment!
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3D shape is important!
OK. Fine. So the shape of the active site is importantHow is the shape formed?
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Formation of active sites
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Active site review
Small part of total enzyme
3D architecture is importantSpecific residues importantNot necessarily contiguous residues
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How does an active site form?
Protein must “fold”into structureHow does protein “fold?”
First, understand protein compositionProteins made up of _____________
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What is an amino acid?
Molecule with _____ group and ___________ group
Each amino acid has a different “R” groupThere are _____ different amino acids
H2
NCOOH
C
R
H
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Amino acids, pH and charge
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Amino acid titration curve
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Asp titration curve
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Amino acids in cells…
H2
NCOOH
C
R
H
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The Peptide bond: Joining amino acids
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Nomenclature: Nt -> Ct
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Charge on peptides is cumulative
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OK. What does this all have to do with enzymes?
What is needed for proteins to fold correctly?Can we design experiment to test?