Studies on the intracellular localization and incorporation of 59Fe into catalase in rat liver

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Abstract
The intracellular distribution of catalase in rat liver has been examined. Catalase activity was greater in the 100,000 g supernatant than in mitochondria and was independent of the concentration of sucrose in the homogenizing media. Catalase was eluted from mitochondria by washing with 0.25 M- or 0.33 M-sucrose solution, but not with 0.88 M-sucrose. In experiments both in vivo and in vitro, the Fe59 radioactivity in catalase isolated from the 100,000 g supernatant fraction of rat liver was higher than in that from mitochondria. The incorporation of Fe59 into haem in vitro occurred more actively with mitochondria than with other subcellular fractions. Under conditions favourable for the incorporation of [2-C14]giycine into proteins in vitro in the absence of mitochondria, preformed Fe59-labelled haemin was incorporated into catalase. It is suggested that mitochondria have a role in the biosynthesis of haem prosthetic groups of catalase.