Question

Which of the following metals is required as cofactor by all enzymes utilising ATP in phosphate transfer? (a) \(\mathrm{K}\) (b) \(\overline{\mathrm{Ca}}\) (c) \(\mathrm{Na}\) (d) \(\mathrm{Mg}\)

Short answer

Magnesium (\text{Mg}) is the metal that is required as a cofactor by all enzymes that utilize ATP in phosphate transfer.

Step-by-step solution

Understanding the Role of Cofactors in Enzyme Action

Cofactors are non-protein chemical compounds that are required for the biological activity of some proteins, such as enzymes. They can be metal ions or organic molecules and are often essential for the normal function of enzymes. Cofactors can assist in performing the reaction by stabilizing the enzyme or even participating directly in the chemical reaction.

Identifying the Cofactor for ATP Utilising Enzymes

Enzymes that facilitate the transfer of a phosphate group from ATP (adenosine triphosphate) to another molecule—a process known as phosphorylation—commonly require a metal ion as a cofactor. This metal ion aids in stabilizing the negative charges that develop on the substrate and the enzyme during the transfer process.

Selecting the Correct Metal Cofactor

Magnesium (Mg) is the metal ion that is most commonly required as a cofactor by enzymes that utilize ATP in phosphate transfer. Mg2+ interacts with ATP to form a complex that is more reactive, aiding in the phosphorylation process by enzymes.

Key concepts

Phosphate Transfer

Phosphate transfer is a critical chemical process in cells, where a phosphate group is moved from one molecule to another. It's fundamental in various metabolic pathways, including those that generate or use adenosine triphosphate (ATP). Enzymes that catalyze these reactions often rely on the presence of a phosphate group donor, typically ATP itself, and a suitable recipient molecule.

In the biological context, the transfer of a phosphate group often activates or deactivates specific proteins or opens up pathways to create energy. For ATP-utilizing enzymes, ensuring the precise and controlled transfer of the phosphate group is crucial for maintaining cellular function and supporting life-sustaining biochemical reactions.

• ATP is the main energy currency in cells, storing and providing energy through the transfer of its phosphate groups.
• Enzymes speed up the transfer of phosphate groups from ATP to target molecules, a process crucial for energy metabolism.

ATP Utilising Enzymes

ATP-utilising enzymes, also known as ATPases, play a pivotal role in the cell as they are involved in various processes, including muscle contraction, nerve impulse propagation, and active transport across cell membranes. These enzymes harness the energy released from the hydrolysis of ATP, which is the breakdown of ATP into adenosine diphosphate (ADP) and a free phosphate group, releasing energy.

ATPases are highly specific in their function and require precise alignment of ATP within the active site for effective catalysis. The presence and proper orientation of ATP are critical for the enzyme's activity and the subsequent energy release, which is then used to carry out itss cellular processes.

Notable Points About ATPases:

• They are essential for moving ions across the cell membrane, affecting muscle, heart, and nerve functions.
• Defects in these enzymes can lead to significant physiological and neurological issues.

Magnesium Role in Phosphorylation

Magnesium (Mg) is an important mineral in the body that plays a vital role in the phosphorylation process, a type of chemical reaction that is central to most cellular processes. As a cofactor, magnesium primarily helps in stabilizing the structure of ATP. It does so by forming a complex with ATP, known as the magnesium-ATP complex, which is more reactive and hence, more efficient in the enzymatic process.

The presence of magnesium reduces the repulsion between the negatively charged phosphate groups of ATP, thereby increasing the potential for the phosphate group to be transferred to a substrate molecule. This facilitation is essential for the proper function of many ATP-utilizing enzymes in cellular metabolism and is why magnesium is a necessary cofactor in these reactions.

Important Aspects of Magnesium's Role:

• It assists in forming and stabilizing the activated substrate-enzyme complexes.
• Optimal magnesium levels are critical for numerous enzymatic reactions in the body, affecting overall health and energy production.