The aim of this study is to teach enzymes, which are one of the biology subjects in understanding which students have a big difficulty, to pre-service teachers through POE method in the case of catalase, which is an oxidoreductase. Descriptive analysis method was employed in this study in which 38 second grade pre-service teachers attending Uludag University Faculty of Education Department of Science Teaching in the spring semester of the 2014-2015 academic year and taking the "General Biology Laboratory" course participated. Four worksheets based on the POE method were used for data collection. The titles of these worksheets are "The Effect of Catalase", "Catalase Concentration", "Relationship between Catalase Concentration and Surface Increases in a Liver Piece", and "Can Catalase Be Re-used?". Frequency (f) and percentage (%) values were taken into consideration in data analysis. Certain results were obtained in the present study in regard to the effect of catalase on H[subscript 2]O[subscript 2] (hydrogen peroxide), catalase concentration, and enzyme-substrate relationship and enzyme-surface area relationship. The averages calculated based on the answers given by the students to the questions asked to them in relevant stages indicate that success rate was 88.58% in the predict stage, 61.18% in the observe stage, and 87.72% in the explain stage while the overall success rate of the POE method was 79.16% for the activity entitled, "The Effect of Catalase"; 64.25% in the predict stage, 75.75% in the observe stage, and 81.58% in the explain stage while the overall success rate of the POE method was 73.86% for the activity entitled, "Catalase Concentration"; 93.86% in the predict stage, 98.68% in the observe stage, and 97.37% in the explain stage while the overall success rate of the POE method was 96.64% for the activity entitled, "Relationship between Catalase Concentration and Surface Increases in a Liver Piece"; and 83.55% in the predict stage, 88.6% in the observe stage, and 87.5% in the explain stage while the overall success rate of the POE method was 86.55% for the activity entitled "Can Catalase Be Re-used?