Peroxisomal remnant structures in Hansenula polymorpha pex5 cells can develop into normal peroxisomes upon induction of the PTS2 protein amine oxidase

have analyzed the properties of peroxisomal remnants in Hantsenula polymorp ha pex5 cells. In such cells PTS1 matrix protein import is fully impaired. In H. polymorpha pex5 cells, grown on ethanol/ammonium sulfate, conditions that repressed the PTS2 protein amine oxidase (AMO), peroxisomal structures were below the limit of detection. In methanol/ammonium sulfate-grown cell s, normal peroxisomes are absent, but a few small membranous structures wer e observed that apparently represented peroxisomal ghosts since they contai ned Pex14p. These structures were the target of a Pex10p.myc fusion protein that was produced in pex5 cells under the control of the homologous alcoho l oxidase promoter (strain pex5::P-AOX.PEX10.MYC). Glycerol/methanol/ammoni um sulfate-grown cells of this transformant were placed in fresh glucose/me thylamine media, conditions that fully repress the synthesis of the Pex10p. myc fusion protein but induce the synthesis of AMO. Two hours after the shi ft Pex10p.myc-containing structures were detectable that had accumulated ne wly synthesized AMO protein and which during further cultivation developed in normal peroxisomes. Concurrently, the remaining portion of these structu res was rapidly degraded. These findings indicate that peroxisomal remnants in pex5 cells can develop into peroxisomes. Also, as for normal peroxisome s in H. polymorpha, apparently a minor portion of these structures actually take part in the development of these organelles.