Deficiency of peroxisome assembly in a mutant of the methylotrophic yeast Hansenula polymorpha

Summary We have isolated a mutant of the metholotrophic yeast Hansenula polymorpha defective in peroxisomal biosynthesis. The mutant strain has been derived by a selection procedure from cells of a high-copy number transformant that overproduces the major peroxisomal enzyme methanol oxidase (MOX) and forms enlarged peroxisomes. In contrast to the parental strain the mutant lacks intact peroxisomes in thin sections, but exhibits electron-dense particles that are devoid of intact membranes and crystalloid cores. Consequently, peroxisomal enzymes show severe proteolytic degradation in crude cell lysates. Complementation of this, and analogous mutations, will offer the possibility to identify genes that are required for peroxisome assembly.