Xref: utzoo sci.bio:2342 sci.chem:499 sci.med:12483
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From: djm@castle.ed.ac.uk (D Murphy)
Newsgroups: sci.bio,sci.chem,sci.med
Subject: Re: Butane death
Message-ID: <469@castle.ed.ac.uk>
Date: 22 Sep 89 08:58:23 GMT
References: <89262.194442RAV103@PSUVM.BITNET> <3398@kitty.UUCP> <4633@ursa-major.SPDCC.COM>
Reply-To: djm@castle.ed.ac.uk (D Murphy)
Organization: Edinburgh University Chemistry
Lines: 29

In article <4633@ursa-major.SPDCC.COM> dyer@ursa-major.spdcc.COM (Steve Dyer)
 writes:
>
>I had always understood that methemoglobin is simply an oxidized form
>of hemoglobin, with the ferrous iron (Fe++) in heme oxidized to the
>ferric (Fe+++) state.  I don't see where methane comes in.  Methane
>certainly isn't one of the traditionally-enumerated toxic agents which
>cause methemoglobinemia, such as nitrites and certain aromatic amines.
>
>-- 
>Steve Dyer

No. There is no iron oxidation in the hemoglobin - oxyhemoglobin reaction.
If there were there would be significant risk of Fe(III) precipitation in
the (mildly) alkaline blood.

What happens is that the first oxygen (there are 4 heme units per molecule)
complexes with the Fe(II) in one of the hemes, causing it to move slightly
out of the plane of the heme. This causes a small conformational change
which assists the uptake of an oxygen molecule by the next heme and so on
until all 4 are occupied. The reverse is also true - oxygen release is
facilitated by the conformational change when one heme releases its O2.

What's more, the oxygen remains intact. If the iron oxidized, oxygen
radicals would be produced which would do lots of damage. Also, a lot of
energy would likely be required to bring about release of O2 at the
tissues.

Murff...