Question

The role of the metal ion (Mg2+) in catalysis by enolase is to: A) act as a general acid catalyst. B) act as a general base catalyst. C) facilitate general acid catalysis. D) facilitate general base catalysis. E) stabilize protein conformation.

Answer 1

Answer: To facilitate general base catalysis. Thus option D is correct.

Step-by-step explanation:

Enolase enzyme is classified as a metalloenzyme that performs the catalytic reaction of converting 2-phosphoglycerate to phosphoenolpyruvate. Various kinetic and spectroscopic methods were used to investigate the role of the divalent Mg+2 metal ions (magnesium ions) involved in the reaction. Both ions were shown to coordinate to the carboxyl group of the substrate and the product. The coordination ensures the stability of the intermediate steps in the general base catalysis of enolase(extraction of the proton by the base) and thus the maximum activity of the dimeric molecule.

An enzyme is a molecule that acts as a catalyst, while ions are believed to facilitate the action of the enzyme .Therefore, options a and b are invalid. The reaction involves the extraction of the proton from the base, not the acid, so option C is incorrect. The transition state and intermediate phases are stabilized, facilitating base catalysis, so option E is wrong.

Answer 2

The correct answer is option D

Step-by-step explanation:

The enzyme enolase is categorized as a metalloenzyme that carries out the catalytic reaction of 2-phosphoglycerate to phosphoenolpyruvate conversion. Several kinetic and spectroscopic methods have been applied to study the role of the divalent metal ions Mg+2 (magnesium ions) involved in the reaction. Both the ions have been shown to coordinate with the carboxylic group of the substrate and product. The coordination provides stability to the intermediate steps in the general base catalysis of enolase (proton abstraction by a base), thereby providing maximum activity to the dimeric molecule.

The enzyme is a molecule that acts as a catalyst while the ions are supposed to facilitate the action of the enzyme. So, option a and b are incorrect. In the reaction, the proton abstraction takes place by a base, not an acid and so, option C is incorrect. The transition state and the intermediate steps are stabilized which facilitates the base catalysis and so, option E is incorrect.