IMMUNOELECTRON MICROSCOPIC OBSERVATION OF THE BEHAVIORS OF PEROXISOMAL ENZYMES INDUCIBLY SYNTHESIZED IN AN N-ALKANE-UTILIZABLE YEAST-CELL, CANDIDA-TROPICALIS

We reported that immunoelectron microscopy was an excellent tool for d etermining the subcellular localization of thiolase isozymes, acetoace tyl-CoA thiolase (T-I) and 3-ketoacyl-CoA thiolase (T-III) in n-alkane -grown Candida tropicalis cells (KAMASAWA, N. et al., (1992). Cell Str uct. Funct., 17: 203-207). Current investigation on the visualization of other peroxisomal enzymes, acyl-CoA oxidase (ACO), catalase (KAT), carnitine acetyltransferase (CAT), isocitrate lyase (ICL) and malate s ynthase (MS), showed that ACO localized in peroxisomes, KAT in peroxis omes and cytoplasm, and CAT in peroxisomes, mitochondria and cytoplasm . Most of ICL and MS were found in peroxisomes. These results agreed w ith previous biochemical studies and supported the presumed roles of t hese enzymes. The same technique was applied to study the process of s ynthesis and localization of these enzymes early in the cultivation pe riod in n-alkane medium when peroxisomes began to proliferate. ACO and T-III were rapidly induced after transfer of cells from glucose- to n -alkane-media. There was a drastic change of their location from cytop lasm to peroxisomes between 1 h and 2 h after the transfer, while T-I, KAT and CAT were moderately induced in cytoplasm and their location w as gradually changed to each organelle. ICL and MS, the key enzymes in the glyoxylate cycle, were already localized in peroxisomes in the gl ucose-grown cells and respective inducible enzymes also were gradually localized there. This visual analysis is useful for the vivid elucida tion of the process of peroxisome proliferation and enzyme transport w ithin a cell.