Biochemistry - Amino Acid Metabolism - Discussion

Phenylketonuria is associated with the aromatic amino acid - phenyalanine. Here, this amino acid is nt converted to L- tyrosine, as a result of the deficiency of the enzyme - phenylalanine hydroxylase.

Class PKU is cause by lack of PAH which involved in conversion of Phenylalanine into Tryosine.

Phenylalanine can't be converted to tyrosine and phenylalanine accumulates. So alternate pathways are operated. Phenylpyruvate, phenyllactate and phenylacetate is excreted in urine. Person is mentally retarded and will have tremors, convulsions, etc and is hypopigmented. Phenyllactic acid in sweat may lead to mousy body odour.

Disease conditions in amino acid metabolism is usually due to the lack of certain enzymes, phenylketonuria is due to the lack of phenylalanine hydroxylase, which is the enzyme involved in the conversion of phenylalanine to tyrosine. While ALkaptonuria is due to the lack of homogentisate dioxygenase in the conversion of Homogentisate to Maleylacetoacetate both of which are intermediates in the total conversion of phenylalanine to acetoacetyl coA.