WATERMELON GLYOXYSOMAL MALATE-DEHYDROGENASE IS SORTED TO PEROXISOMES OF THE METHYLOTROPHIC YEAST, HANSENULA-POLYMORPHA

We have studied the fate of the watermelon (Citrullus vulgaris Schrad. ) glyoxysomal enzyme, malate dehydrogenase (gMDH), after synthesis in the methylotrophic yeast, Hansenula polymorpha. The gene encoding the precursor form of gMDH (pre-gMDH) was cloned in an H. polymorpha expre ssion vector downstream of the inducible H. polymorpha alcohol oxidase promoter. During methylotrophic growth, pre-gMDH was synthesized and imported into peroxisomes, where it was enzymatically active. The appa rent molecular mass of the protein located in H. polymorpha peroxisome s was equal to that of pre-gMDH (41 kDa), indicating that N-terminal p rocessing of the transit peptide had not occurred in the yeast.