The Hansenula polymorpha per6 mutant is affected in two adjacent genes which encode dihydroxyacetone kinase and a novel protein, Pak1p, involved in peroxisome integrity.

The Hansenula polymorpha per6-210 mutant is impaired in respect of growth on methanol (Mut-) and is characterized by aberrant peroxisome formation. The functionally complementing DNA fragment contains two open reading frames. The first encodes dihydroxyacetone kinase (DAK), a cytosolic enzyme essential for formaldehyde assimilation; the second ORF codes for a novel protein (Pak1p). We have demonstrated that per6-210 cells lack DAK activity, causing the Mut- phenotype, and have strongly reduced levels of Pak1p, resulting in peroxisomal defects. Sequence analysis revealed that per6-210 contains a mutation in the 3' end of the DAK coding region, which overlaps with the promoter region of PAK1. Possibly this mutation also negatively affects PAK1 expression.