Abstract
Peroxisomes play a role in lipid mobilization or photorespiration in higher plants. Most peroxisomal proteins are synthesized in the cytosol and transported into peroxisomes depending on two types of targeting signal, PTS1 and PTS2. PTS1 is the most common targeting signal of peroxisomal proteins that is defined as the C-terminal tripeptide. PTS2 is a nonapeptide which is located within the N-terminal presequence. The presequence is cleaved in peroxisomes, but the mechanism of the cleavage has not been clarified.
AtDeg15 (At1g28320) is a homologue of E.coli DegQ protease which has a PTS1-like C-terminal sequence. We analyzed an Arabidopsis mutant containing a T-DNA insertion in AtDeg15. Immunoblot analysis showed that the mutant atdeg15 accumulated precursors of PTS2-containing enzymes, such as thiolase and malate dehydrogenase. Furthermore, atdeg15 was defective in β-oxidation during seed germination. These results suggested that AtDeg15 is a processing peptidase of PTS2 presequences and is involved in lipid degradation.
