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chymotrypsin
- Mr 25,000
- cleaves carboxy side of Phe, tyr, trp
- catalyzes hydrolysis of esters, amides, etc.
- 241 aa
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how is chymotrypsin activated
- requires 2 cleavages13 and 16, 146 and 149
- folding brings amino acid site together
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active site of chymotrypsin
- covalent catalysis
- acid/base catalysis
- transition state stabilitzation
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elements involved in the covalent catalysis in chymotrypsin
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protease families
- serine proteases
- cysteine proteases (papain)
- metalloproteases
- aspartyl proteases
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realtion HIV to protease
- HIV proteaes break down viral synthesized polyproteins.
- Inhibitors of HIV protease interrupt the virus life
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Charactersitics of regulatory proteins
- how the cell turns up or down
- multi-subunit enzymes
- rarely just on/off
- different kinetic problems
- increase or decrease activity in response to signal
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Types of regulatory enzymes
- Allosteric
- Covalent modifications
- regulatory proteins
- proteolytic activation(chymotrypsin)
- regulatory cascades (blood clotting)
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allosteric enzymes
- -Modulators (activators and inhibitors)
- -homotropic (substrate=modulator)
- -heterotrophic (substrate does not equal modulator)
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good description of enzyme mechanism
- sequence of steps
- structure of each intermediate and transition state
- rates of intermediate interconversion
- interaction between enzyme and intermediates and transition states
- energetic contributions of all groups
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evidence for covalent catalysis
- pre-steady state kinetics
- substrates with different ractivities
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zymogen
- an inactive precursor
- becomes active after cleavage
- regulated by proteolytic cleavage
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protein kinase
an enzyme that modifies other proteins by adding a phsophate group
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fibrinogen pathway
fibrinogen-fibrin monomer-fibrin polymer-cross linked fibrin polymer
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what activate fibrinogen
thrombin
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what makes the cross linked fibrin polymer
Factor XIII
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what protease is heavily involved in fibrin pathway
serine protease
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How many and what are the two pathways of of Fibrinogen
- extrinsic and intrinsic pathway
- intrinsic: all in the blood steam
- extrinsic: all in the blood stream except Tissue factor pathway (TFP) acts first TFP released by damage
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what ion is heavily involved in the fibrogen pathway
calcium is required in many steps
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