Molecular Characterization of Two Genes with High Similarity to the Dihydroxyacetone Synthase Gene in the Methylotrophic Yeast Pichia methanolica

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The methylotrophic yeast Pichia methanolica possesses two genes, PmDAS1 and PmDLP1, whose amino acid sequences show high similarity to dihydroxyacetone synthase (DAS), the formaldehyde-fixing enzyme for methanol metabolism within the peroxisome. The PmDAS1 and PmDLP1 genes encode 709 and 707 amino acid residues respectively, and PmDas1p contains a type-1 peroxisomal targeting signal (PTS1), while PmDlp1p does not. Upon phylogenetic analysis, PmDas1p fit into the DAS group with other DASs, while PmDlp1p was grouped with the DAS-like proteins (DLP) of non-methylotrophic yeasts and fungi, a branch of the phylogenetic tree independent of the DAS and transketolase (TK) groups. While expression of PmDAS1 restored the methylotrophic growth of the Candida boidinii das1Δ strain, the PmDLP1 and PmDAS1−ΔPTS1 genes did not. Taken together, these results indicate that PmDAS1 encodes a functional DAS and has an indispensable role in methanol metabolism, and that PmDlp1p share a common, as yet uncharacterized function in P. methanolica as well as in non-methylotrophic yeasts and fungi.