Which substrate is used in the CK assay to activate the enzyme?

In the creatine kinase (CK) assay, the substrate that activates the enzyme is creatine. Creatine plays a crucial role in the assay because CK catalyzes the phosphorylation of creatine to generate phosphocreatine, a high-energy molecule used in muscle cells. This reaction is essential for assessing CK activity, which is often relevant in diagnosing myocardial infarction or muscle disorders.

Adenosine, N-acetylcysteine, and glucose do not serve as substrates for the CK enzyme in the context of its assay. While N-acetylcysteine is an antioxidant that can be used in various biochemical reactions, it does not directly relate to the activation of CK in the assay setup. Therefore, creatine is the correct substrate to consider when discussing the activation of CK in the assay, making it essential for accurately measuring the enzyme's activity.