A newly discovered function of peroxisomes: involvement in biotin biosynthesis

In plants, peroxisomes are the organelles involved in various metabolic processes and physiological functions including β-oxidation, mobilization of seed storage lipids, photorespiration, and hormone biosynthesis. We have recently shown that, in fungi and plants, peroxisomes play a vital role in biosynthesis of biotin, an essential cofactor required for various carboxylation and decarboxylation reactions. In fungi, the mutants defective in peroxisomal protein import exhibit biotin auxotrophy. The fungal BioF protein, a 7-keto-8-aminopelargonic acid (KAPA) synthase catalyzing the conversion of pimeloyl-CoA to KAPA in biotin biosynthesis, contains the peroxisomal targeting sequence 1 (PTS1), and its peroxisomal targeting is required for biotin biosynthesis. In plants, biotin biosynthesis is essential for embryo development. We have shown that the peroxisomal targeting sequences of the BioF proteins are conserved throughout the plant kingdom, and the Arabidopsis thaliana BioF protein is indeed localized in peroxisomes. Our findings suggest that peroxisomal localization of the BioF protein is evolutionarily conserved among eukaryotes, and required for biotin biosynthesis and plant growth and development.