(DEC 2002)
12. When a mixture of protease, protein, nuclease and nucleic acid are incubated at 37^OC, at the end of one hour which will remain intact
(1) Nucleic acid                                                     (2) Nuclease
(3) Protein                                                            (4) protease

The correct answer is (2) Nuclease.

Introduction

When a mixture of protease, protein, nuclease, and nucleic acid is incubated at physiological temperature (37°C), different components behave differently due to their structural stability and enzymatic activity. Understanding which molecules remain intact after incubation helps in grasping concepts of biochemical stability, enzyme function, and molecular degradation. This article provides a thorough explanation by analyzing the effects of protease and nuclease enzymes on proteins and nucleic acids under incubation conditions.

Proteins and Proteases

• Proteins: Polymers of amino acids that fold into specific three-dimensional structures; sensitive to proteolytic cleavage.

• Proteases: Enzymes that catalyze the hydrolysis of peptide bonds in proteins, breaking them down into smaller peptides or amino acids.

• At 37°C, proteases are active and will degrade proteins in the mixture.

Nucleic Acids and Nucleases

• Nucleic acids: DNA and RNA molecules composed of nucleotide sequences; carry genetic information.

• Nucleases: Enzymes that hydrolyze phosphodiester bonds between nucleotides, degrading nucleic acids.

• At 37°C, nucleases are active and degrade nucleic acids.

Scenario Analysis

Given the presence of both proteases and nucleases in the mixture, and substrates (proteins and nucleic acids):

• Proteases will target and digest proteins present.

• Nucleases will degrade nucleic acids.

• Both enzymes remain active around 37°C as this is near physiological temperature.

After 1 hour incubation:

• Proteins will be degraded by proteases.

• Nucleic acids will be degraded by nucleases.

• Proteases are enzymes themselves (made of protein) and may remain active for some time but can undergo autolysis or denaturation.

• Nucleases are enzymes as well, but generally more stable and may remain intact for longer.

Which Remains Intact?

• Nuclease is most likely to remain intact because it can resist degradation longer than proteases and still be active at 37°C.

• Proteins and nucleic acids will be significantly degraded.

• Protease enzymes might degrade themselves (autolysis) or other proteins, shortening their lifespan.

Supporting Points

• Proteases are designed to degrade proteins rapidly.

• Nucleases specifically target nucleic acids, sparing proteins.

• 37°C is the optimum—stable—temperature for many enzymes, including nucleases.

• Stability varies, but nucleases often resist longer action at physiological temperature.

Summary Table

Conclusion

After incubation of a mixture containing protease, protein, nuclease, and nucleic acid at 37°C for one hour, nuclease is most likely to remain intact. Proteins and nucleic acids will be degraded by protease and nuclease, respectively, while proteases may begin to degrade themselves or lose activity. This understanding is vital in studies involving enzymatic degradation, molecular biology experiments, and clinical biochemistry.