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From: davison@menudo.uh.edu (Dan Davison)
Subject: Re: I stand corrected (was Re: Where do herbivores get their amino acids?)
In-Reply-To: karl@spruce.gsfc.nasa.gov's message of 16 May 91 14: 19:15 GMT
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Date: Fri, 17 May 1991 19:57:00 GMT

   |> Nope, it's nine.  The essential: histidine, isoleucine, leucine,
   |> lysine, methionine, phenylalanine, threonine, tryptophan, valine.
   |> The non-essential: alanine, arginine, asparagine, aspartate,
   |> cystenine, glutamate, glutamine, glycine, proline, serice, and
   |> tyrosine.

   Table 21-1 lists arginine along with the ones you give as essential.

   Is this the current understanding, Dan?

Hmmm.  Mathews and Van Volde list 10, the nine above plus arginine.
(p. 681).  Leningher lists those 10. White, Handler and Smith list
those 10. Voet and Voet list those 10.  The difference appears to be
rate-dependent and opinion-dependent . The most mammals *do*
synthesize arginine, so it is not essential in that the aa cannot be
synthesized. But rats do not synthesize enough and all mammals break
arginine down to urea as part of the urea cycle, so there just isn't
enough around for normal growth. 


So, there are two classes of "essential" as used in the textbooks: 1)
able to be synthesized de novo and 2) able to get enough for normal
growth demands.

dan
--
dr. dan davison/dept. of biochemical and biophysical sciences/univ. of
Houston/4800 Calhoun/Houston,TX 77054-5500/davison@uh.edu/DAVISON@UHOU
Disclaimer: As always, I speak only for myself, and, usually, only to
myself.