Activation of a peroxisomal Pichia pastorisd-amino acid oxidase, which uses d-alanine as a preferred substrate, depends on pyruvate carboxylase

Abstract d-Amino acid oxidase (DAO) is an important flavo-enzyme that catalyzes the oxidative deamination of d-amino acids into the corresponding α-keto acid, ammonia and H2O2. We identified two amino acid oxidases in the methylotrophic yeast Pichia pastoris: Dao1p, which preferentially uses d-alanine as a substrate, and Dao2p, which uses d-aspartate as a preferred substrate. Dao1p has a molecular mass of 38.2 kDa and a pH optimum of 9.6. This enzyme was localized to peroxisomes, albeit a typical peroxisomal targeting signal is lacking. Interestingly, P. pastoris mutant strains, defective in the enzyme pyruvate carboxylase, showed a pronounced growth defect on d-alanine, concomitant with a significant reduction in Dao1p activity relative to the wild-type control. This indicates that pyruvate carboxylase functions in import and/or activation of P. pastoris Dao1p.