Hydrogen Peroxide

[K]

"Hydrogen is a by-product of many metabolic proccesses."

1. Which metabolic processes?
2. What is the chemistry behind it?

I've searched the net, but they all seem to explain about the industrial processes, whereas I need to know about the intracellular reactions (mainly in plants). Could anyone explain this or give me a link to a suitable site?

Thanks.

[kk]

As far as I know, amine oxidases release H2O2 as a side product of their catalytic activity. In humans, these are MAO, PAO, DAO, SSAO/VAP-1, and the LOX family of enzymes.

I have some questions too:

Are there any other enzymes producing H2O2 in humans?
Could someone specify where these reactions are located (intracellularly or extracellularly)? LOXes work extracellularly on collagen and elastin substrates. But in peroxisomes, there are also H2O2 producing reactions going. Where else?

And another question, how easily does H2O2 diffuse across the plasma membrane?

[jonmoulton]

Here's a key source.

http://en.wikipedia.org/wiki/Superoxide_dismutase

[MrMistery]

asides from SOD i think that's most of the important ones. And i think the K value for H2O2 is similar to that of water, perhaps a bit slower. but it definitely moves by simple diffusion - there are no H2O2 transport proteins