The correct answer is (3) Enzymes are not inhibited irreversibly by heavy metals such as Hg2+, Ag+.

Introduction

Enzyme inhibition is a key regulatory and toxicological aspect of enzymology. Heavy metals like Hg2+2+ and Ag++ are well known to irreversibly inhibit many enzymes by binding strongly to sulfhydryl or other active site groups. Meanwhile, monoclonal antibodies capable of catalyzing hydrolysis of esters and carbonates represent a unique class of catalytic antibodies (abzymes) with enzymatic activity. This article clarifies these points to correct misconceptions often encountered regarding enzyme inhibition and antibody catalysis.

Analysis of the Statements

(1) Allosteric enzymes function through reversible noncovalent binding of allosteric modulators or effectors.

• True:

  • Allosteric modulators bind non-covalently at regulatory sites, reversibly altering enzyme activity.

  • This is fundamental to allosteric regulation and dynamic enzymatic control.

(2) Monoclonal antibodies that catalyze hydrolysis of esters or carbonates can be produced.

• True:

  • Catalytic monoclonal antibodies (“abzymes”) can be generated to catalyze specific chemical reactions, including ester and carbonate hydrolysis.

  • These are produced via immunization with transition state analogs and engineered for catalytic function.

(3) Enzymes are not inhibited irreversibly by heavy metals such as Hg2+2+, Ag++.

• False:

  • Heavy metals like mercury and silver ions frequently cause irreversible inhibition by covalently binding to critical thiol groups or other functional groups, permanently disabling enzyme activity.

  • Such irreversible inhibition is well documented in biochemistry and toxicology.

(4) Acid phosphatases hydrolyze biological phosphate esters at ~ pH 5.0.

• True:

  • Acid phosphatases exhibit optimal activity in acidic conditions close to pH 5.

  • This behavior is consistent with the enzyme’s role and classified by pH preference.

Supporting Details on Heavy Metal Inhibition

• Heavy metals form strong bonds with cysteine sulfhydryl groups.

• These interactions permanently alter enzyme structure and block catalytic functions.

• This is different from reversible inhibitors which bind non-covalently and dissociate.

Overview of Catalytic Monoclonal Antibodies (Abzymes)

• Artificially created antibodies recognizing transition state analogs.

• Exhibit enzyme-like catalytic activities.

• Useful in research, diagnostics, and as potential therapeutics.

Summary Table

Conclusion

The incorrect statement is (3). Enzymes are irreversibly inhibited by heavy metals such as Hg2+2+ and Ag++, owing to their strong covalent interactions with enzyme functional groups. The other statements accurately reflect enzyme behavior and emerging concepts like catalytic antibodies.