Week 10 Key
- Given the substrates and catalysts, write out the mechanism
for this enzyme.
- Explain this mechanism in catalytic terms.
- Show reasonable electron movements for bond making/breaking
in this mechanism.
- Key catalytic mechanism is covalent catalysis:
- Formation of thiohemiacetal makes abstraction of hydride
- Immediate oxidation product, enzyme thioester, captures oxidation
energy in form of high energy bond.
- General base catalysis aids formation of thiohemiacetal by
making thiol a better nucleophile.
- General acid catalysis (by same group as general base above)
aids nucleophilic attack by phosphate on thioester by protonating
sulfide leaving group.
- Draw a "Kinetic Mechanism Diagram" for this reaction.
- Note the symmetry of the addition and release of substrates/products.
- Correlate the kinetic and chemical mechanisms.
- Is "NAD" order consistent with catalytic mechanism? Rationalize by need of NAD before going ahead with tying up Ga-3-P
©R A Paselk
Last modified 25 March 2011