The proteasome is a high molecular weight, multisubunit and multicatalytic enzyme. Here we report the purification and characterization of ostrich skeletal muscle 20S proteasome. It was purified to homogeneity with Mr 700 000, pI 6.67 and a ladder of 22.2 33.5 kDa bands on SDSPAGE. The amino acid composition and aminoterminal sequences showed large identities to those of other species. For the three major activities, pH and temperature optima ranged between 8.0 11.0 and 40 70C, and stabilities between 5 12 and up to 40 60C. Substrate specificity and inhibitory effects were also studied. Many similarities to other sources were shown, with a few significant differences.
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