Substrate-level phosphorylation

<p>Substrate-level phosphorylation is a metabolism reaction that results in the production of <a href="/facts/Adenosine_triphosphate/nB9bwgcU">ATP</a> or <a href="/facts/Guanosine_triphosphate/NAwoHjTW">GTP</a> supported by the energy released from another high-energy bond that leads to phosphorylation of <a href="/facts/Adenosine_diphosphate/JEDnsCjn">ADP</a> or <a href="/facts/Guanosine_diphosphate/3BkkMql3">GDP</a> to ATP or GTP (note that the reaction catalyzed by creatine kinase is not considered as "substrate-level phosphorylation"). This process uses some of the released <a href="/facts/Chemical_energy/Y3VP3Ifq">chemical energy</a>, the <a href="/facts/Gibbs_free_energy/bvenDuzh">Gibbs free energy</a>, to transfer a <a href="/facts/Phosphoryl/HU9n4lgV">phosphoryl</a> (PO3) group to ADP or GDP. Occurs in <a href="/facts/Glycolysis/a5ApxLoG">glycolysis</a> and in the citric acid cycle.
</p><p>Unlike <a href="/facts/Oxidative_phosphorylation/en2l08P9">oxidative phosphorylation</a>, oxidation and phosphorylation are not coupled in the process of substrate-level phosphorylation, and reactive intermediates are most often gained in the course of <a href="/facts/Oxidation/Pyd5RVcj">oxidation</a> processes in <a href="/facts/Catabolism/CFWUdphX">catabolism</a>. Most ATP is generated by oxidative phosphorylation in <a href="/facts/Aerobic_respiration/kb6gpsvL">aerobic</a> or <a href="/facts/Anaerobic_respiration/IMSY03HG">anaerobic respiration</a> while substrate-level phosphorylation provides a quicker, less efficient source of ATP, independent of external <a href="/facts/Electron_acceptor/sRvhMXqH">electron acceptors</a>. This is the case in human <a href="/facts/Erythrocyte/Kggpq8Jh">erythrocytes</a>, which have no <a href="/facts/Mitochondrion/ErHqrdJ1">mitochondria</a>, and in oxygen-depleted muscle.
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Substrate-level phosphorylation open-in-new

Substrate-level phosphorylation