adenosine 5'-(trihydrogen diphosphate) 58-64-0 ADP

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This adenine nucleotide (FWfree-acid = 504.16 g/mol; CAS 58-64-0; Molar Absorptivity = 15,400 M–1cm–1, l = 259 nm) is a product in ATPdependent transphosphorylases, phosphohydrolases, and molecular motors; as such, ADP often inhibits these enzymes. Enzymatic Phosphorylation: ADP is a substrate for adenylate kinase (Reaction: ADP2– + MeADP " MeATP2– + AMP) and other enzymes that stabilize ATP concentrations in prokaryotes [e.g., acetate kinase (Reaction: MgADP + Acetyl-phosphate ! MeATP2– + Acetate)] and eukaryotes [e.g., pyruvate kinase (Reaction: MgADP + Phosphoenolpyruvate ! MgATP2– + Pyruvate), creatine kinase (Reaction: MgADP + Creatine-phosphate ! MgATP2– + Creatine), arginine kinase (Reaction: MgADP + Arginine-phosphate ! MgATP2– + Arginine), and nuclecleotide diphosphate kinase (Reaction: ADP2– + MgGTP2– " MgATP2– + GDP2–)]. ATP Synthase: ADP is a primary substrate for the FOF1 ATP synthase (Reaction: MgADP + Pi + High Chemiosmotic Gradient Energization State ! MgATP2– + Low Chemiosmotic Gradient Energization State). ADP can also become entrapped within a catalytic site of the rotary motor, when proton motive is low, absent, or uncoupled, and its inhibitory action under such conditions is believed to prevent wasteful hydrolysis of ATP (Reaction: MgATP2– + H2O MgADP + Pi). Metal Ion Binding Properties: As a polyanion, ADP not only binds physiologic divalent cations Mg2+ and Ca2+, but also forms reversible complexes with Mn2+ and Co2+. For reversible complexation of ADP2– with a metal ion Me2+, (Reaction: ADP2– + Me2+ ! MeADP), Kformation = [MeADP]/[ADP2–]free[Me2+]free, indicating that [MeADP]/[ADP2– ]free = Kformation ′ [Me2+]free. In many cases, metal-free ADP is not a substrate and instead acts as a revesible inhibitor. Good experimental design therefore demands rigorous control of free metal ion concentration to control the ratio of metal-bound and metal-free forms. When exposed to Cr(III) at elevated temperature, ADP also forms ligand exchange-inert complexes with Cr3+. Platelet Aggregation: ADP is also a well-known activator of platelet aggregation, as mediated by the ADP receptors P2Y1, P2Y12 and P2X1. Upon conversion to adenosine by ecto-ADPases, platelet activation is inhibited by means of adenosine receptors. Target(s): Hydrogenomonas facilis ribulosediphosphate (RuDP) carboxylase and NADH-, ATP-dependent CO2 fixation; platelet (Na+/K+)-ATPase; hydrogen-ion transport in chloroplasts; pyruvate dehydrogenase kinase; 5-oxo-L-prolinase, or L-pyroglutamate hydrolase; a-NADHdependent reductase, rat liver microsomes; nitrogenase; Trypanosoma cruzi hexokinase; maize leaf acetyl-coenzyme A carboxylase; rat brain mitochondrial calcium-efflux; sarcoplasmic reticulum Ca2+ ATPase; Na+-Na+ exchange mediated by (Na+/K+)ATPase reconstituted into liposomes; nitrate and nitrite assimilation in Zea mays under dark conditions; PGE1-activated platelet adenylate cyclase in rats and rabbits; mitochondrial F1-ATPase, inactive complex formed upon binding ADP at a catalytic site; ATP-sensitive K+ channels, frog skeletal muscle; human 5-phosphoribosyl-1pyrophosphate synthetase; Crithidia fasciculata glutathionylspermidine synthetase; myosin V ATPase; cystic fibrosis transmembrane conductance regulator (ABC transporter) via its adenylate kinase activity; V type ATPase/synthase.