Investigation of the Energy Requirement and Targeting Signal for the Import of Glycolate Oxidase into Glyoxysomes

The uptake of glycolate oxidase into peroxisomes has been studied using an in vitro import system. Import of glycolate oxidase was found to be ATP‐dependent and temperature‐dependent and specific for glyoxysomes. In these respects it resembles the import of isocitrate lyase into both glyoxysomes and leaf‐type peroxisomes; thus the ATP‐dependence and temperature dependence appear to be general properties of plant microbody protein import. Two mutant versions of glycolate oxidase were prepared lacking 59 amino acids of the N‐terminus and 53 amino acids of C‐terminus, respectively. Both were capable of ATP‐dependent import, whereas a fusion protein consisting of the cytosolic protein dihydrofolate reductase linked to the last 20 amino acids of glycolate oxidase bound to glyoxysomes but did not enter the organelle.