Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!sdd.hp.com!wuarchive!udel!haven.umd.edu!mimsy!dftsrv!spruce.gsfc.nasa.gov!karl From: karl@spruce.gsfc.nasa.gov (karl anderson) Newsgroups: sci.bio Subject: I stand corrected (was Re: Where do herbivores get their amino acids?) Message-ID: <1991May16.101915@spruce.gsfc.nasa.gov> Date: 16 May 91 14:19:15 GMT References: <1991May16.030620.24749@menudo.uh.edu> Sender: news@dftsrv.gsfc.nasa.gov Reply-To: karl@spruce.gsfc.nasa.gov (karl anderson) Distribution: usa Organization: NASA/GSFC code 923 Lines: 46 In article <1991May16.030620.24749@menudo.uh.edu>, davison@menudo.uh.edu (Dan Davison) writes: |> In article <1991May14.102820@quercus.gsfc.nasa.gov> |> karl@quercus.gsfc.nasa.gov (Karl Anderson) writes: |> |> Human metabolism can synthesize all but seven (the "essential" |> amino acids) of the twenty; they must get those seven from |> their food. |> [..] |> |> 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. |> |> How did you get 7? I don't see any interconversion pathways in |> humans listed...perhaps you were counting salvage pathways? |> |> source: Stryer, "Biochemistry", 3d. ed, pg. 578. |> |> I just finished teaching this a few weeks ago! |> Um, I should have checked my copy of Stryer (1st ed). On page 503 he says "Humans can synthesize only half the basic set of twenty amino acids (Table 21-1). These amino acids are called nonessential, whereas the ones that must be supplied in the diet are called essential. These terms refer to the needs of an organism under a particular set of conditions. For example, enough arginine is synthesized by the urea cycle to meet the needs of an adult but not those of a growing child. A deficiency of even one amino acid results in a *negative nitrogen balance* [Stryer's emphasis]. In this state, more protein is degraded than is synthesized, and so more nitrogen is excreted than is ingested." Table 21-1 lists arginine along with the ones you give as essential. Is this the current understanding, Dan? The figure 7 was dredged up from imperfect memory - I took biochem 12 years ago. Thanks for giving us an authoritative answer to the original question. I think this group needs more of this kind of rigor. -- Karl A. Anderson | Internet: karl@forest.gsfc.nasa.gov NASA/GSFC code 923 (STX) | voice: (301) 286-3815 Greenbelt, MD 20771 | #include "std_disclaimer"