What are the functions of ATP?

There are several functions of ATP. One function is to assist in the transport of molecules and ions across the cell membrane (active transport). Additional functions of ATP include intracellular signaling, Puringeric signaling, DNA and RNA synthesis, synaptic signaling, the circulation of blood, and providing energy for muscle contraction. 

ATP is crucial for signal transduction, as ATP acts as a substrate for kinases. During phosphorylation a signaling cascade becomes activated, and begins regulating different intracellular pathways. Magnesium ions help regulate the kinase activity in cells. Additionally, ATP helps trigger intracellular messenger release. These messengers include hormones, neurotransmitters, lipid mediators, different enzymes, and reactive oxygen species. For example, ATP may act as a substrate for adenylate cyclase. When binded to adenylate cyclase, ATP converts the molecule to cyclic AMP (cAMP). cAMP plays a role in releasing calcium from intracellular storage, as well as regulating ion channels, and activating protein kinases. 

ATP is required for DNA and RNA synthesis to be carried out. ATP is one of four nucleotide-triphosphate monomers that is required during RNA synthesis. In DNA synthesis, ATP becomes transformed through the removal of an oxygen atom from the sugar to create deoxyribonucleotide, dATP.    

ATP is also necessary for muscle contraction and has 3 main roles. The first role is creating the force against adjacent actin filaments through the cycling of myosin cross-bridges. ATP’s second role is assisting in pumping calcium ions located in the myoplasm across the sarcoplasmic reticulum. This is done against their concentration gradients using active transport. The third function is the active transport of sodium and potassium ions across the sarcolemma so that calcium ions may be released when the signal is received. 

Purinergic signaling is a form of paracrine signaling that uses extracellular ATP. ATP is released from vesicular storage and regulated by IP3. ATP is stored and released among neurotransmitters. It can induce various pringeric responses such as control of autonomic functions, neural glial interactions, and control of vessel tone.