These studies don't seem to support that FM and ME/CFS are one and the same. For example, in the ME/CFS study only 1 of the 25 participants had either low valine or threonine, but the FM study says lower levels of valine and threonine were significant. Also, only 5 of the 25 ME/CFS patients had low methionine, which would seem to suggest that a deficiency in that essential amino acid is not particularly telling. I'm also curious as to how protease deficiency could cause low tryptophan in ME/CFS but (in my case at least) normal serotonin. There are also other studies ( http://jop.sagepub.com/content/19/4/385.short and http://submit.clinsci.org/cs/105/0213/cs1050213.htm ) that make the opposite finding as the one you listed, with high levels of tryptophan in ME/CFS patients. Also my phenylethylamine and dopamine levels were normal and high-normal respectively, which would also not seem indicative of a problem with the digestion of phenylalanine. The study you cited also shows that none of the ME/CFS patients had low levels of histidine, although this is also a essential amino acid. I guess I'm a bit confused as to whether you are saying that you think all proteases are lacking, or just specific ones cleaving certain amino acids?