Biochemistry Enzyme Properties and Nomenclature

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Questions and Answers

At what temperature is the ideal storage condition for LDH (LD4 and LDS) enzymes?

Room temperature

What is the effect of hemolysis on enzyme concentration?

Increase

What type of inhibition occurs when a molecule binds to an enzyme's active site, preventing substrate binding?

Competitive inhibition

What is the main function of the Enzyme Commission (EC)?

To standardize enzyme nomenclature Signup and view all the answers

What is the effect of lactescence or milky specimens on enzyme concentration?

Decrease Signup and view all the answers

What is the optimal temperature for substrate and coenzymes?

8°C Signup and view all the answers

What type of inhibitor binds to the enzyme-substrate (ES) complex, resulting in increased inhibition with increasing substrate concentration?

Uncompetitive Inhibitor Signup and view all the answers

What are enzymes with the same catalytic reactions but slightly different molecular structures called?

Isoenzymes Signup and view all the answers

What is the optimal temperature for enzymatic activity?

37°C Signup and view all the answers

What is the temperature coefficient (Q10) that describes the increase in enzyme activity with temperature?

A two-fold increase in enzyme activity for every 10°C increase in temperature Signup and view all the answers

What pH range is typical for most physiologic reactions?

pH 7-8 Signup and view all the answers

What effect does refrigeration/freezing have on enzymes?

Reversible inactivation Signup and view all the answers

What is the effect of increasing enzyme concentration on the rate of reaction?

The rate of reaction increases. Signup and view all the answers

What happens to the reaction rate when substrate concentration reaches a maximal value?

The reaction rate no longer increases. Signup and view all the answers

What is the function of coenzymes in enzymatic reactions?

They increase the velocity of an enzymatic reaction. Signup and view all the answers

What is the term for enzymes that have the same function but differ in their molecular structure?

Isoenzymes. Signup and view all the answers

What is the effect of pH on enzyme activity?

Enzyme activity is pH-dependent, with optimal activity at a specific pH range. Signup and view all the answers

What is the effect of temperature on enzyme activity?

Enzyme activity increases with temperature up to an optimal point, then decreases. Signup and view all the answers

Study Notes

Enzyme Storage and Stability

Enzymes can be preserved for a longer period at -20°C due to the inactivation of enzymes.
8°C is the ideal temperature for substrate and coenzymes.
Room temperature is suitable for storing LDH (LD4 and LDS).

Enzyme Inhibition and Activation

Hemolysis increases enzyme concentration, whereas lactescence or milky specimens decrease enzyme concentration.
Inhibitors can bind to the enzyme-substrate complex, increasing inhibition with increasing substrate concentration.

Enzyme Nomenclature

The Enzyme Commission (EC) standardized enzyme nomenclature in 1961, with revisions in 1972 and 1978.
Enzymes are classified based on their biochemical functions, substrate, and reaction catalyzed, with a unique EC number.
The first digit of the EC number places the enzyme into one of six classifications.

Enzyme Classification

Oxidoreductases catalyze redox reactions (e.g., CO, LDH, MDH, ICD, G-6-PD).
Uncompetitive inhibitors bind to the enzyme-substrate complex, increasing inhibition with substrate concentration.

Isoenzymes

Isoenzymes have the same catalytic reaction but slightly different molecular structures.
Fractionating isoenzymes enhances the importance of total enzyme activity.

Temperature Effects

Increasing temperature usually increases the rate of chemical reactions by increasing molecular movement.
Enzymes are active at 25°C, 30°C, or 37°C, with 37°C being the optimum temperature for enzymatic activity.
The rate of denaturation increases with temperature, and is significant at 40°C-50°C.
Refrigerated/freezing temperatures can reversibly inactivate enzymes.
Repeated freezing and thawing can denature proteins and should be avoided.
The temperature coefficient (Q10) indicates a two-fold increase in enzyme activity for every 10°C increase in temperature.

pH Effects

Extreme pH levels can denature an enzyme or cause structural changes, affecting its ionic state.
Most physiologic reactions occur in the pH range of 7-8.

Enzyme Basics

Enzymes are proteins produced by living cells that catalyze chemical reactions in organic matter.
Enzymes are measured by their activity, not absolute values.
Enzymes are large molecules confined within cells unless membrane permeability allows them to enter the blood.
Abnormal enzyme levels in serum can indicate organ damage.

Factors Affecting Enzyme Reactions

Enzyme concentration: higher enzyme concentration increases the reaction rate.
Substrate concentration: the reaction rate increases with substrate concentration until saturation kinetics.
Cofactors: nonprotein entities that must bind to particular enzymes before a reaction occurs (e.g., NADP).
Coenzymes: organic compounds that increase the velocity of an enzymatic reaction when their concentration increases.

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Description

This quiz covers the properties of enzymes, including ideal storage temperatures and the effects of hemolysis and lactescence on enzyme concentration. It also touches on the Enzyme Commission's classification system.