Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In enzymology, an adenosine kinase (EC 2.7.1.20) is an enzyme that catalyzes the chemical reaction ATP + adenosine \rightleftharpoons ADP + AMP. Thus, the two substrates of this enzyme are ATP and adenosine, whereas its two products are ADP and AMP. This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing groups (phosphotransferases) with an alcohol group as acceptor. The systematic name of this enzyme class is ATP:adenosine 5'-phosphotransferase. This enzyme is also called adenosine kinase (phosphorylating). This enzyme participates in purine metabolism.