Xref: utzoo sci.chem:2002 sci.bio:3600
Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!usc!apple!rutgers!ub!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.chem,sci.bio
Subject: Re: Thermodynamics of reduction of phosphate to phosphine
Summary: Biological production of phosphine
Keywords: marsh gas, wierd organisms
Message-ID: <4067@kitty.UUCP>
Date: 30 Sep 90 00:18:09 GMT
References: <60883@iuvax.cs.indiana.edu>
Organization: Recognition Research Corp., Clarence, NY
Lines: 75

In article <60883@iuvax.cs.indiana.edu>, chiaravi@copper.ucs.indiana.edu (Lucius Chiaraviglio) writes:
> 	Something that has intrigued me (and some microbiologists) for a while
> is the process, so far as I know almost completely uncharacterized, of
> phosphine production in marshes.  Most of marsh gas is methane and carbon
> dioxide, but it also contains hydrogen sulfide and can contain small amounts
> of phosphine (PH[3]), and probably also traces of P[2]H[4], since marsh gas
> can auto-ignite upon contact with air.
> ...
> However, no organisms have yet been found which produce
> phosphine, or P[2]H[4] for that matter, and we remain completely ignorant of
> the biochemistry of this process.

	Phosphine has long been known as an end product of putrefaction,
especially putrefaction occuring under water or in damp locations.  As an
interesting coincidence, phosphine has an odor which resembles that of
decaying fish smothered in garlic.  [yummmy] :-)

	It is my belief that an explanation of the mechanism behind the
biological production of phosphine requires consideration of the various
processes involved in putrefaction.  It is also my feeling that there
exists more than one putrefactive mechanism for the production of phosphine.

	The following represents pure *speculation* on my part with respect
to a *possible* mechanism for production of phosphine as a consequence of
putrefaction:

	Consider that the majority of phosphoglycerides are phosphatidates.
Further consider that E. coli and other bacteria produce phosphatidylserine
from L-serine and (I believe) cytidine diphosphoacylglycerol.

	Putrefaction chiefly involves deamination and/or decarboxylation.
The decarboxylation products of phosphatidylserine are carbon dioxide and
phosphatidylethanolamine.  While free serine apparently will not undergo
decarboxylation (or deamination, for that matter), the phosphatidyl form
will.

	It is therefore my speculation that as a putrefactive process,
phosphine results from the successive decarboxylation of phosphatidylserine,
through phosphatidylethanolamine, eventually into phosphine (and perhaps,
diphosphine).

	I know of no reference to support this speculation, but I suspect
a modest amount of literature research will readily prove or disprove its
feasibility.

> 	Phosphate seems to be the most likely source of the phosphorus in
> phosphine, given that it is by far the most common phosphorus-containing
> compound (for that matter, has anyone heard of any other naturally-occurring
> phosphorus-containing compounds found in nature, except for the phosphine and
> P[2]H[4]?).

	While most biological phosphorous is in the form of phosphate
esters and diesters, there are some exceptions.  Consider as an example,
2-aminoethylphosphonic acid, which is found in some protozoa.

> To make it
> simpler, assume that they use hydrogen gas as the reductant -- many organisms
> actually do use hydrogen gas at partial pressures of <0.01 atm, and common
> internally-used reductants such as NADH are thermodynamically not too far from
> equilibrium with the corresponding oxidized compound (such as NAD+) and
> hydrogen gas at low partial pressure.

	I don't believe that any free hydrogen under any biological
conditions is going to result in, or otherwise aid, the formation of
phosphine.

> and/or would someone
> like to take a crack at this problem themselves?

	Why don't you do a little investigation along the lines I suggested?
If you publish a paper as a result, you can include a note of thanks.  :-)

Larry Lippman @ Recognition Research Corp.  "Have you hugged your cat today?"
VOICE: 716/688-1231   {boulder, rutgers, watmath}!ub!kitty!larry
FAX:   716/741-9635                  {utzoo, uunet}!/      \aerion!larry