[Neutral proteinase in peroxisomes from rat liver cells]

A proteinase with a pH optimum of 7.6 and Mr of 43 kD has been isolated from rat liver peroxisomes. The peroxisomes were shown to possess an intrinsic mechanism responsible for the degradation of proteins, e.g., catalase. Some physico-chemical properties and turnover parameters of neutral proteinase from peroxisomes (i.e., synthesis rate, lifetime, degradation of the newly synthesized enzyme) were studied. In terms of enzymatic and immunologic properties, the enzyme under study is similar to mitochondrial and cytosolic proteinases responsible for the initial inactivation of catalase in subcellular structures.