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From: sdyer@bbncc5.UUCP (Steve Dyer)
Newsgroups: net.med
Subject: Re: Nutrasweet(psychological problems?)
Message-ID: <235@bbncc5.UUCP>
Date: Wed, 24-Jul-85 09:36:10 EDT
Article-I.D.: bbncc5.235
Posted: Wed Jul 24 09:36:10 1985
Date-Received: Tue, 20-Aug-85 00:31:23 EDT
References: <617@gatech.CSNET>
Organization: Bolt Beranek and Newman, Cambridge, MA
Lines: 40

> 	  In relation to aspartame, however, the problem is not simply that
> 	  one of its metabolites is pheylalanine, rather it is that a portion
> 	  of aspartame "looks" very similar to pheylalanine, and as a result
> 	  could have a tendency to enter the dopamine pathway itself, if it
> 	  can get into the brain without being metabolized.  The odds of this
> 	  happening are very good, since aspartame is rather cyclic and the
> 	  pheylalanine "part" is rather exposed, making it available for active
> 	  transport past the blood brain barrier and making the pheylalanine
> 	  "part" available for interaction with dopamine related receptor sites. 
> 

Interesting.  Has this been studied?  Is there any evidence for competition
for the phenylalanine pathway?  Is there any evidence that the stuff passes
through the blood-brain barrier unchanged?   My first guess would be that
the various hydroxylase and decarboxylase enzymes involved in 
neurotransmitter production would be fairly specific for a plain-old
amino acid, and would not be fooled by a peptide.  But, anyway, this is
my speculation.  I am surprised that studies of this sort haven't been
done in the almost 13 years since aspartame was synthesized.  Do you
have any studies you can refer me to, or is this just an educated guess
as well?

> 	  Remember that when aspartame was being first developed, it was
> 	  described as a new amino acid derivative with unique properties.
> 	  Aspartame in actuality is a brand new amino acid, not ever seen
> 	  before in this universe.  It is difficult to predict how the CNS
> 	  will respond to a brand new amino acid that possesses unique 
> 	  properties as well as being physically similar to amino acids
> 	  that the brain is currently using for its normal function.
> 

I would claim that it's stretching it a bit to identify aspartame as a "new"
amino acid, because it is simply the methyl ester of a two-peptide
amino acid chain consisting of phenylalanine and aspartic acid.  I would
agree that certainly the aspartame molecule is new, but is it also the
case for the conjugation of phenylalanine and aspartic acid?
-- 
/Steve Dyer
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