The specific and constant presence of 2,5-dihydroxyphenylpyruvic acid (2,5-DHPPA), an imaginary intermediary metabolite of phenylalanine and tyrosine in the urine of collagen disease patients, has been spotted by us1 on the one-dimensional ascending paper chromatogram, although the existence of the substance of 2,5-DHPPA is itself thought deniable by La Du et al.,2,4 and the specificity of the spot to collagen disease is negated by Tye et al.,5 who consider the spot due to salicylic acid derivatives. The spot that has been determined by us as 2,5-DHPPA or its lactone6 on paper chromatogram still lacks biochemical evidences to confirm the absolute identification.Aside from the disputes concerning the substance of 2,5-DHPPA, the facts that the clinical and laboratory status of collagen disease are undoubtedly alleviated by a low phenylalanine and tyrosine diet,7 and aggravated by the administration of 1-tyrosine in their active stage, have been established
NISHIMURA N, MAEDA K, YASUI M, OKAMOTO H, MATSUNAKA M, TOSHINA H. Phenylalanine and Tyrosine in Collagen Diseases: Urinary Excretion of General Intermediary Metabolites of Tyrosine in Patients with Collagen Disease and Liver Disease. Arch Dermatol. 1961;83(4):644–652. doi:10.1001/archderm.1961.01580100108015
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