Degradation of aromatic amino acids in Candida maltosa

Abstract

AbstractThe degradation of l‐ and d‐aromatic amino acids has been studied in Candida maltosa. The following main metabolites were indentified: indolelactate was the degradation product of tryptophan, phenylpyruvate and phenyllactate were that of phenylalanine and p‐hydroxyphenylpyruvate and p‐hydroxyphenyllactate resulted from degradation of tyrosine. The first step of utilization of l‐aromatic amino acids was found to be a transamination. The cells contained increased aromatic aminotransferase activity if grown on medium supplemented with one of the three l‐aromatic amino acids. Three aromatic aminotransferases were separated by DEAE‐cellulose chromatography. The pathway for degradation of d‐aromatic amino acids involves deamination as the initial step. The enzyme was characterized to be a general d‐amino acid oxidase capable of utilizing various d‐amino acids. Synthesis of this enzyme was constitutive. Common products of both enzymatic reactions with the aromatic amino acids were the corresponding aromatic pyruvates. Formation of the aromatic lactate derivatives was catalyzed by an aromatic lactate dehydrogenase. This enzyme possessed a high substrate specificity for p‐hydroxyphenylpyruvate, phenylpyruvate, and indolepyruvate and was synthesized constitutively.