This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Four Formulas, Subject name: Biochemistry
Which of the following enzyme catalyses the formation of AMP from two molecules of ADP? 
Select and explain. 
A. Adenylate kinase, B. Adenylyl cyclase, C. Adenosine kinase, D. Adenosine deaminase
A: Adenylate kinase
Answer: A: Adenylate kinase 
Explanation: When ATP level is reduced, AMP is formed by Adenylate kinase reaction. 2 ADP - ATP + AMP This is why AMP is an allosteric activator of glycolysis. Adenylate kinase or myokinase is a phosphotransferase. It catalyses the interconversion of adenine nucleotides (ATP, ADP, and AMP). It plays an impoant role in cellular energy homeostasis.