I’m thinking about this question regarding kinases and I’m not sure if I have the right answer. What do kinases use as an energy source? Is the answer ATP?
You can think of an ATP as an ADP and a phosphate bound together. It is the bond between the ADP moiety and the phosphate moiety that is the highest-energy bond in the molecule. If the terminal phosphate of ATP is transferred to a protein (releasing free ADP) then the system is in a lower-energy state that was the initial ATP and un-phosphorylated protein. That release of energy helps drive the reaction to the ADP & phosphoprotein side.
Not every kinase will use ATP as a substrate. Other high-energy phosphates are available in cells and there are many kinases.
