|WikiProject Molecular and Cell Biology||(Rated Start-class, Low-importance)|
the effect of xanthine oxidase activities on ethanol metabolism
From the article
- Xanthine oxidase is really the product of a proteolytic cleavage of the enzyme xanthine dehydrogenase, which occurs in tissues under conditions of oxygen starvation. When oxygen supply is restored to the tissue, xanthine oxidase activity continues, and the result is the liberation of free radicals that can cause the injury known as "ischemic reperfusion damage." Xanthine oxidase is the first enzyme known that completely reverses its catalytic activity upon modification by proteases.
"The protein is large, having a molecular weight of 270,000...." I'd like to know where this information came from since every protein database I can find says its actually around 146,000. Someone should change it. (19.08.08)
Bovine Xanthine Oxidase
Anyone know about the effects of homogenisation of milk on Bovine Xanthine Oxidase. Non-digestion and damage to blood vessels caused by activity on plasmogen in artery walls.
Homogenization and ingested XO
www.mercola.com/2002/jul/10/milk_heart.htm [Unreliable fringe source?] This article] talks about the idea that homogenization causes fat globules to surround XO and somehow avoid the natural breakdown of this enzyme into its base amino acids in the stomach, allowing it passage into the bloodstream, where it somehow causes heart damage. So umm... should I include this? Can someone hopefully tell me where this theory is wrong? Wouldn't fat globules simply be digested? I can't see how it would somehow perfectly seal off an enzyme and not deconstruct it, because I thought fats were broken down into fatty acids and reassembled. Tyciol 06:00, 10 December 2006 (UTC)
- i dont see how such a large (huge!) molecule would be able to cross into the bloodstream without being broken down, even if it successfully passed through the stomach, so i guess we can just forget about that. --Echosmoke 22:23, 12 November 2007 (UTC)
- also, thats a whacko site --Echosmoke 22:28, 12 November 2007 (UTC)
Reaction (as posted)
The following chemical reactions are catalyzed by xanthine oxidase: hypoxanthine + H2O + O2 xanthine + H2O2 xanthine + H2O + O2 uric acid + H2O2
It was my understanding that the above reactions are not 100% accurate, as hypoxanthine and xanthine do not directly produce a H2O2 byproduct. Instead the equations should have superoxide production followed by (fast) degradation of superoxide into hydrogen peroxide. But this would not happen without the presence of superoxide dismutase, so really the equations should look like:
hypoxanthine + H2O + O2 <->(XO) xanthine + .O2- <->(SOD) xanthine + H2O2 xanthine + H2O2 + O2 <->(XO) uric acid + .O2- <->(SOD) uric acid + H2O2
Right now the sources I have confirming this are Invitrogen, a company that produces an assay for X/XO reactions, as well as Kuppusamy P and Zweier JL, 1989, an article that explores the production of free oxygen radicals including .O2-, H2O2, and .OH.
Paragraph two says "Xanthine oxidase is defined as an enzyme activity". Can this be correct? Surely it is a substance, not a process. Perhaps it should be 'Xanthine oxidase is defined by its enzyme activity'?