2084411647

2084411647 - Reaction Rates of Enzymes are Affected by pH...

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1 BSCI230-Lecture5 Enzymes and Membranes Topic 4-5: Chp. 3, 4 G Reaction Rates of Enzymes are Affected by pH Constant: E concentration S concentration S ubstrate P roduct E nzyme In the simplest terms the Rx goes But remember the enzyme forms a complex with its substrate To continue the catalysis the enzyme must be released, thus: • The reaction is better represented by the following equation: k 1 k 3 E free + S ES E free + P k 2 k 4 where k 1 through k 4 are rate constants, ES is the Enzyme-substrate Complex , and E free is the free (unbound) form of the enzyme. Enzyme activity: is measured as the velocity (concentration/time) of the conversion of a specific substrate by an enzyme. Formulation of the kinetics is defined by Michaelis- Menten Michaelis–Menten Equation v = V max [S] K m + [S] v = initial velocity of product formation [S] = initial substrate concentration V max = maximal possible reaction velocity K m = kinetic parameter: ( k 2 + k 3 )/ k 1
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2 Experimentally get Initial Velocity at Constant Enzyme Concentration Michaelis-Menten Plot of Enzyme-catalyzed RX Linearizing the Michaelis– Menten Graph • Covert hyperbolic curve into straight line by taking double reciprocal of the Michaelis–Menten equation. v = V max [S] 1 = [S] + K m K m + [S] vV max [S] Rearranging gives: 1 = K m × 1 + 1 max [S] V max The Lineweaver–Burk Equation 1 = K m × 1 + 1 max [S] V max Straight Line equation: y = m x + b; where m = slope and b = y intercept Thus; slope = K m / V max ; y intercept = 1/ V max , and the x intercept = –1/ K m Lineweaver-Burk Plot: Double reciprocal of M-M expression
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This note was uploaded on 10/22/2008 for the course BSCI 207 taught by Professor Higgins during the Spring '08 term at Maryland.

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2084411647 - Reaction Rates of Enzymes are Affected by pH...

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