W27 L1 - Enzyme Specific Activity and Turnover Number Flashcards

Flashcards based on enzyme lecture notes focusing on specific activity and turnover number.

What is the general scheme of enzyme function?

Enzyme binds substrate, forms enzyme-substrate complex, reaction occurs to form product and regenerate the enzyme.

What is Vmax?

The maximum speed of an enzymatic reaction when all enzyme is in the enzyme-substrate complex.

What does Vmax depend on?

Enzyme concentration. More enzyme, higher Vmax.

What is Km?

The affinity of the enzyme; depends exclusively on rate constants.

Does Km depend on enzyme concentration?

No, Km is independent of enzyme concentration.

What does Vmax tell us?

How the enzyme behaves at very high substrate concentrations.

What does Vmax/Km tell us?

How the enzyme behaves at very low substrate concentrations.

Why can't Vmax or Vmax/Km be used to compare enzymes directly?

Because they depend on enzyme concentration.

What are specific activity and turnover number?

Two parameters that are independent of enzyme concentration.

What is the unit for specific activity?

Mole of substrate / (second * gram of protein).

What is catalytic activity?

Mole of substrate converted per second.

How is catalytic activity calculated?

Multiply Vmax by the volume of the reaction.

How does specific activity relate to enzyme purity?

Specific activity increases with the purity of the enzyme.

What is the molecular mass of the enzyme?

100 kilodaltons, or 100,000 grams per mole.

What does the turnover number tell us?

How many molecules of substrate one molecule of enzyme can convert per second.

What is another name for Turnover Number?

kcat

What is a typical range for turnover number?

Between 100 per second and 1,000,000 per second.

Is the turnover number dependent on enzyme concentration?

No, the turnover number (kcat) is not dependent on enzyme concentration.

Which parameters can be used to compare enzymes?

Specific activity and turnover number (kcat) can be used to compare enzymes.

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