Adenosinedifosfaat

Adenosinedifosfaat, known in English as adenosine diphosphate (ADP), is a nucleotide composed of the nucleoside adenosine linked to two phosphate groups. It participates in cellular energy transfer and metabolism. In cells, ADP arises mainly from the hydrolysis of ATP and is converted back to ATP by phosphorylation when energy is required, via ATP synthase using inorganic phosphate during oxidative phosphorylation and photosynthesis, or by substrate-level phosphorylation in glycolysis. The cellular energy charge is governed by the ATP/ADP/AMP system; adenylate kinase catalyzes the reversible reaction 2 ADP ⇌ ATP + AMP, helping balance energy supply during fluctuating demand.

ADP is abundant in the cytosol and intermembrane space; the mitochondrial ADP/ATP translocase exchanges ADP from the cytosol with ATP produced in the matrix, closing the energy loop.

Outside cells, ADP acts as a signaling molecule in purinergic signaling, notably in platelets where ADP promotes aggregation by activating P2Y receptors (P2Y1 and P2Y12) on platelets, and can influence vascular tone and inflammation via other P2 receptors.

Adenosinedifosfaat is a universal metabolite, and disturbances in its metabolism affect energy homeostasis and metabolic diseases. Drugs that modify purinergic signaling targeting ADP-induced platelet activation (for example P2Y12 antagonists) are used in preventing thrombosis.