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Modes of Enzymatic Catalysis

Modes of Enzymatic Catalysis. _________________ modes General _______________ Catalysis __________________ Catalysis ___________________ modes ______________________ Effects __________________________________. 1. Chemical Modes of Catalysis. A. General Acid-Base Catalysis.

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Modes of Enzymatic Catalysis

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  1. Modes of Enzymatic Catalysis • _________________ modes • General _______________ Catalysis • __________________ Catalysis • ___________________ modes • ______________________ Effects • __________________________________

  2. 1. Chemical Modes of Catalysis A. General Acid-Base Catalysis • Reaction acceleration is achieved by catalytic __________________ • A general _______ (B:) can act as a __________________________ • Can remove a proton from water and thereby generate the equivalent of OH- in neutral solution • Can produce a stronger nucleophilic reactant (X:-)

  3. A-X + E X-E + A X-E + B B-X + E B. ________________________ Catalysis • A general ________ (BH+) can __________________ • A covalent bond may break more easily if one of its atoms is protonated (below) • All or part of a substrate is _________ covalently to the enzyme to form a reactiveintermediate • Can be used for ______________________________

  4. Example: Sucrose phosphorylase Stepone: a glucosyl residue is transferred to enzyme Steptwo: Glucose is donated to phosphate *(Sucrose is composed of a glucose and a fructose) 2. _________________ of Enzymatic Catalysis Binding forces utilized for catalysis – _______________________ _______________________________________________________ 1. Charge-charge interactions 2. Hydrogen bonds 3. Hydrophobic interactions 4. Van der Waals forces

  5. A. The Proximity Effect - __________________________ substrate molecules in the active site (1) Reduces their degrees of freedom (2) Results in a ___________________________________ (3) The relative _______________________ (“effective molarity”) predicts the rate acceleration expected due to this effect

  6. Transition-State (TS) Stabilization transition states bind more • tightly than substrates • The enzyme ____________________, forcing it toward TS • An enzyme must be complementary to the TS • Enzymes may bind their transition states _____________ times more tightly than their substrates

  7. Transition-state (TS) __________________ • Stable compounds whose structures resemble _____________ _________________________ • 2-Phosphoglycolate, a TS analog for the enzyme triose phosphate isomerase • Can be used medically as _______________________________

  8. ________________________ Reactions • Enzyme rates can approach the _____________________ of the rate of diffusion of two molecules in solution • Under physiological conditions the encounter frequency is about 108 to 109 M-1s-1 • A few enzymes have rate-determining steps that are roughly as fast as the binding of substrates to the enzymes Triose Phosphate Isomerase (TPI)

  9. Properties of ________________________ • Includes Trypsin, Chymotrypsin,Elastase • Many digestive proteases similar in ________________ structure • Chymotrypsin, trypsin and elastase - _______________ structure • Active site substrate specificities differ due to relatively small differences in __________________________________

  10. Serine Proteases Use Chemical and Binding Modes of Catalysis ______________ (__ amino acids) - ____ ____ ____

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