Biochemistry Lec 12 (PAR2): Enzyme Kinetics (Michaelis-Menten & Lineweaver Burk Plot)

How does high temperature affect enzyme activity?

High temperature means more kinetic energy, which increases the activity, but if the temperature exceeds a certain point, it denatures the protein.

What is optimal pH?

The pH at which the activity in a specific enzyme is highest

The optimal pH range of enzymes is typically between ___________, but exceptions to this rule include...

5 to 9pepsin and the phosphatases (acid and alkaline phosphatase)

How does enzyme concentration affect enzyme activity? What aboud substrate concentration.

Increasing enzyme concentration or substrate concentration increases the rate of reaction up to the point where enzymes exceed substrates or substrates exceeds enzymes.

Michaelis-Menten equation

v = (vmax [S])/(Km + [S])vmax = k2[E] (micro M/min)km = (k-1 + k2)/k1 (constant)Km is independent of [S] and {E]

When [S] is less than Km

Km + [S] is almost equal to Km

When [S] is greater than Km

Km + [S] is almost equal to [S]

When [S] = Km

Vi = Vmax/2

When k-1 is greater than k2

Km = k-1/k1 (dissociation of ES complex)

High vs low Km in Km = k-1/k1

Loose binding in high KmTight binding in low Km

What is Km?

[S] at which half of the enzyme active sites are filled (vi = vmax/2)Determines affinity of enzyme for substrate (substrate specificity)

Lineweaver-Burk plot - know it

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Describe the three types of reversible enzyme inhibitors.

1. Competitive: inhibitor competes with the substrate for active site - just increase [S] to overcome2. Noncompetitive: binds enzyme at different site3. Uncompetitive: only binds to ES complex

True or False: Competitive inhibitors increases Km, while Vmax remains the same.

True

Do NOT memorize inhibitor list.

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True or False: Noncompetitive inhibitor increases Vmax.

False: Noncompetitve inhibitor decreases Vmax by decreasing the function [E].

How does the slope in Weaver-Burk plot compare to the control when uncompetitive inhibitor is added?

Slope is not affected (new line runs parallel to control), but Km and Vmax do both change.