Superoxide synthetases

The plasma-membrane bound superoxide-generating flavoprotein (superoxide synthetase) of human polymorphonuclear neutrophils (PMN) has been solubilized by Triton X-100and deoxycholate and purified. The enzyme catalyses the reaction ... 

Deleterious protein cross-linking can also be induced by reactive nitrogen species (RNS) such as peroxynitrite ONOO formed by the reaction of superoxide with nitric oxide (NO). The cross-links are formed between tyrosine residues following nitration by peroxynitrite (Sitte, 2003). Carnosine appears to play roles not only in NO generation but also in protection against excess NO production by inducible nitric oxide synthetase (NOS), thereby preventing ONOO-mediated protein modification (Fontana et ah, 2002). Evidence for a carnosine-NO adduct has also been published (Nicoletti et al., 2007). 

An effect secondary to the activation of enzymes by increased calcium levels can be increased production of reactive oxygen and nitrogen species. Thus, activation of mitochondrial dehydrogenases increases NADH production and electron transport, yet increased calcium uncouples ATP synthesis, and the excess electron generates superoxide. Calcium also activates nitric oxide synthetase. 

Air embolism in unanaesthetized sheep causes increased permeability, lung oedema associated with oxidant stress ° and increase in thromboxane and prostacyclin in lung lymph and plasma Whereas superoxide dismutase and heparin prevented the increase in lung vascular permeability OKY-046, a thromboxane synthetase inhibitor, did not Therefore, it is conceivable that superoxide anion released from activated neutrophils is causative in this form of lung injury . 

Uchigata Y, Yamamoto H, Kawamura A, Okamoto H (1982) Protection by superoxide dis-mutase, catalase, and poly(ADP-ribose) synthetase inhibitors against alloxan and strepto-uotocin-induced islet DNA strand breaks and against the inhibition of proinsulin synthesis. J Biol Chem 257 6084-6088... 

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