Catalase and Peroxidase in Primary Bean Leavesduring Development and Senescence

Abstract

Summary Catalase and peroxidase activity and isoenzyme composition are assayed in extracts of thedeveloping and senescing primary leaves of Phaseolus vulgaris which are also analysed for their chlorophyll content, organic nitrogen content and soluble protein content. Photosynthetic rate and dark respiration rate are measured in leaves of intact plants. Catalase activity level is highest in the young mature leaf, when also peaks are observed in photosynthetic rate level, dark respiration rate level, chlorophyll content, organic nitrogen content and soluble protein content. Peroxidase activity level gradually increases during development and senescence until the leaves turn brown. The number of anodic peroxidase isoenzymes increases from two in the young growingleaf to four in the senescent leaf. Three cathodic peroxidases were detected in mature and senescent leaves which were most intense at senescence. Only one band with catalase activity was detected which was most intense in the young mature leaf. Catalase and peroxidase activity level in primary bean leaves show an inverse relationship during development and senescence. It is hypothesized from this, from the molecular structure of both enzymes and from the in vitro relationship between catalase and peroxidase activity that the tetrameric molecules of catalase in vivo might desintegrate into monomeric units with peroxidase activity.