Enzyme substrate regulation levels (5) exam 3 EXSC401.txt

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Enzyme substrate regulation levels (5) exam 3 EXSC401.txt
2015-03-09 01:37:47
exsc pfk enzyme substrate regulation km 2vmax
5 levels of enzyme regulation PFK -allosteric Km, 1/2Vmax, E+S E+P
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  1. Enzyme levels of regulation
    • 1. *Substrate supply: when high amts of substrate, LESS likely it will UNBIND b/c of diffusion
    • 2. *Product Inhibition: When Lots of product surrounding enzyme, LESS likely it will allow for more product to form…may encourage the reverse reaction to favor E+S vs E+P. Also product may inhibit Substrate from binding, via competitive inhibition.
    • 3. Allosteric regulation (ie PFK enzyme): utilized in order to regulate speed of reaction occurring, helps to regulate HEAT and Radical Production!
    • 4. Covalent modification (ie phosphorylation/dephos)
    • 5. Genetic regulation (ie phos of TFs via INcrease in activity of SF pathways)
    • *every enzyme subject to these two types of regulation
  2. Example of a enzyme+substrate
    • Hexokinase(enzyme) + glucose and ATP(substrate) (E + S) -> binding of substrates to enzyme (E . S)
    • Hexokinase bound to product (Glucose-6-phosphate and ADP) (E . P) -> Hexokinase + G-6-P + ADP (E + P)
    • Hexokinase has a
  3. Km and 1/2Vmax
    • When the substrate concentration [] does not have to be high in order to get to 1/2Vmax: LoW Km
    • For example, hexokinase moving in the forward reaction does not require high amounts of glucose in order to get to G-6-P: has LOW Km for the substrate
    • Hexokinase + product going backwards to glucose from G-6-P is unlikely, reverse reaction is not favored because there is rarely a buildup of G-6-P, since it is beign used steadily for other pathways: High Km for the product!
  4. PFK enzyme and allosteric regulation
    • Allosteric regulation: By CHANGING the SHAPE of the enzyme, can CHANGE the Binding constant to INCREASE the LIKELIHOOD for Binding
    • AMP with PFK: AMP presence CHANGES the BINDING AFFINITY for the substrate to bind to PFK, Increasing its ability to bind to the substrate (F-6-P and ATP). This gives PFK a LOWER Km
    • Decreasing affinity for substrate to PFK: ATP presence REDUCES Binding Affinity for substrate to bind PFK. In this case, PFK is a HIGH Km enzyme!