Välittäjäentsyymejä

Välittäjäentsyymejä, often translated as mediator enzymes or signaling enzymes, are a group of enzymes that play a crucial role in intracellular signaling pathways. These enzymes act as key players in transmitting signals from the cell surface to the interior, leading to specific cellular responses. They are typically activated by a primary signal, such as a hormone or neurotransmitter binding to a receptor, and then catalyze reactions that modify other molecules within the cell, thereby amplifying and propagating the signal.

A common mechanism involves phosphorylation, where a mediator enzyme transfers a phosphate group from ATP to a target protein. This phosphorylation can alter the target protein's activity, localization, or interaction with other molecules, thus relaying the signal further down the pathway. Kinases and phosphatases are prominent examples of mediator enzymes involved in these phosphorylation/dephosphorylation cycles.

Other types of mediator enzymes include those that generate second messengers, like cyclic AMP (cAMP) or inositol trisphosphate (IP3). These small molecules then diffuse within the cell and activate downstream targets, leading to a cascade of events. Phospholipases, which cleave lipids to produce signaling molecules, also fall into this category. The precise function of a mediator enzyme is context-dependent, varying with the specific signaling pathway and cell type. Their dysregulation can lead to various diseases, including cancer and metabolic disorders, highlighting their fundamental importance in cellular physiology.