The structure and function of acid proteases. VII. Distribution and some properties of acid proteases in monkey...

1. The distribution of acid protease activity in various tissues of Japanese monkey (Macaca fuscata fuscata) was investigated with hemoglobin as a substrate at pH 3.0. The activity per protein weight in crude extracts was highest in spleen and lung, and decreased in the order: spleen, lung greater than kidney, testis greater than brain greater than liver, placenta greater than thyroid gland, muscle. The activity in crude muscle extract was about one-tenth those of spleen and lung. The activity per wet tissue weight was in roughly the same order except for a lower activity per wet weight of brain. 2. Upon chromatography of each crude extract on a Sephadex G-100 column, one major activity peak was eluted at a position corresponding to a molecular weight of about 41,000. This enzyme activity is attributed to cathepsin D [EC 3.4.23.5]. In addition, a minor activity peak was eluted in the case of spleen, lung and kidney at the break-through position, corresponding to a molecular weight of more than 100,000. This activity peak is presumably due to cathepsin E. These acid protease activities were, in most cases, strongly inhibited by pepstatin, an acid protease-specific peptide inhibitor. 3. The distribution of acid protease activity was investigated in the brain of crab-eating monkey (Macaca fascicularis). The activity was fairly evenly distributed among several regions of the brain, and its distribution was similar to those of other acid hydrolases, especially N-acetyl-beta-D-glucosaminidase [EC 3.2.1.30] and acid phosphatase [EC 3.1.3.2], which are marker enzymes of lysosomes.