Sandbox Reserved 1471: Difference between revisions

Cyclooxygenases catalyzes arachidonic acid or other fatty acids into prostaglandin H2 (PGH2) and other molecules that can be used for signal transduction. Of the two catalytic activities, the cyclooxygenase reaction happens before the peroxidase reaction. However, the peroxidase activity activates the cyclooxygenase activity.<ref name="Picot">PMID:8121489</ref> “Two-electron reduction of a peroxide substrate results in the oxidation of the ferric heme to an oxo-ferryl porphyrin radical cation.”<ref name="Rouzer">PMID:18952571</ref> The most important catalytic residue is Tyrosine 385. It transfers and electron to the heme to create the radical on the tyrosine <ref name="Rouzer" /> The tyrosine then takes the pro-S hydrogen from carbon 13 of arachidonic acid to produce a radical on the arachidonic intermediate. <ref name="Lehninger">"Chapter 21: Lipid Biosynthesis." ''Lehninger Principles of Biochemistry'', by David L. Nelson et al., Basingstoke, 2017, pp. 824-825.</ref> Two oxygen molecules are inserted to cyclize the intermediate.<ref name="Lehninger" /> Tyrosine 385 is reduced from the “peroxyl radical to the hyperoxide to form PGG2.”<ref name="Rouzer" /> PGG2 is then reduced by the peroxidase activity to form PGH2. (Lehninger). The Tyrosing 385 radical is regenerated, so the cyclooxygenase activity does not need to be activated for every reaction.<ref name="Rouzer" />