Phenylalanine and Tyrosine in Collagen Diseases: Urinary Excretion of General Intermediary Metabolites of Tyrosine in Patients with Collagen Disease and Liver Disease

Introduction 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 lactone 6 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