Primary structure and expression of peroxisomal acetylspermidine oxidase in the methylotrophic yeast Candida boidinii

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Abstract
Acetylspermidine oxidase (ASOD) belongs to a family of FAD‐containing amine oxidases and catalyzes the oxidation of N‐acetylated spermidine in polyamine metabolism. ASOD was purified to apparent homogeneity from cells of the methylotrophic yeast Candida boidinii grown on spermidine as the sole nitrogen source. C. boidinii ASOD catalyzed the oxidation of only N 1‐acetylspermidine. Based on partial amino acid sequences, oligonucleotide primers were designed for polymerase chain reaction, and the ASOD‐encoding gene, ASO1, was cloned. The open reading frame encoding ASO1 was 1530 bp long and corresponded to a protein of 509 amino acid residues (calculated molecular mass=57 167 Da). ASO1 contained a FAD‐binding motif of ‐A‐‐I‐A‐ in the N‐terminal region and carried an amino acid sequence of ‐S‐K‐L at the C‐terminal, representing a typical peroxisome targeting signal 1. ASOD was localized in the peroxisomes in overexpressed C. boidinii. To our knowledge, this is the first report on the gene coding for ASOD that can catalyze the oxidation of N‐acetylated polyamine as a substrate, from any type of organism.