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ABSTRACT
Catalase enzyme was explored in three methylotrophic yeast strains Pichia pastoris X-33, Hansenula polymorpha CBS 4732 and Pichia pini NBIMCC 8360 during batch-wise growth on different carbon sources. For investigation of compartmentalization of the enzyme within yeast cells a mitochondrial fraction from each strain was isolated. Peroxisomal and mitochondrial import of catalase enzyme was tested quantitatively by subcellular fractionation followed by enzyme activity assays. Efficient catalase import into peroxisomes was observed when cells were cultivated under peroxisome-inducing conditions (i.e. growth on methanol), whereas more significant catalase activity was measured in mitochondria when cells were grown on polyvalent alcohol glycerol that favor respiration and ROS (reactive oxygen species) accumulation within this organelle. When yeast cells utilize glucose the catalase enzyme is relatively equal distributed between the two compartments (peroxisomes and mitochondria). Results indicated that mitochondrial matrix in methylotrophic yeasts possess in situ mechanism for scavenging of ROS represented by Mn SOD and mitochondrial catalase.