Kinases are enzymes that transfer phosphate groups to other proteins; hence they are also denominated phosphotransferases. The process is called phosphorylation and takes place under utilization of nucleosidetryphosphate (ATP) as phosphate donor. The reverse operating enzymes are phosphatases which remove a phosphate from proteins. Phosphorylations often times lead to the activation or deactivation of the phosphorylated enzyme. These enzymes are frequently kinases or phosphateases as well, leading to further downstream phosphorylation events. Such cascades are often found in signaling networks that regulate intracellular processes, such as metabolic pathways. Kinases may also phosphorylate sugars, lipids, amino acids and nucleic acids. As mentioned, the reverse reaction is catalyzed by phosphatases. Also the depolymerization of enzymes, such as DNA and RNA is catalyzed by phosphateses, in this case they are called nucleases.