ISSA Nutritionist Practice Exam 2025 - Complete Preparation Guide

The enzyme that catalyzes the breakdown of ATP (adenosine triphosphate) to ADP (adenosine diphosphate) is ATPase. This enzyme plays a crucial role in energy metabolism, facilitating the release of energy stored in the phosphate bonds of ATP. When ATP is broken down by ATPase, one of the phosphate groups is released, resulting in the formation of ADP and an inorganic phosphate (Pi). This reaction is fundamental to cellular processes since ATP is often referred to as the energy currency of the cell, and its hydrolysis provides the energy required for various biological functions, including muscle contraction, active transport, and biochemical synthesis.

Other enzyme options provided do not participate directly in this process. Hexokinase, for example, is involved in the phosphorylation of glucose to produce glucose-6-phosphate, playing a key role in glycolysis. Amylase is an enzyme that breaks down carbohydrates, specifically starches, into sugars. Creatine kinase is involved in the reversible reaction that helps regenerate ATP from ADP and creatine phosphate in muscle cells, but it does not catalyze the breakdown of ATP itself. Hence, ATPase is specifically responsible for converting ATP to ADP, making it the correct answer