Purification and characterization of yeast protease B.

Protease B [EC 3.4.22.9] was purified from baker's yeast by plasmolysis of yeast, acid activation, acid precipitation, and column chromatographies on QAE-Sephadex, SP-Sephadex, D-tryptophan methyl ester-Sepharose 4B and Sephadex G-100. The purified enzyme was inhibited by phenylmethylsulfonyl fluoride and sulfhydryl-blocking reagents. Chymostatin and antipain at extremely low concentrations (1 micro M) inhibited the protease B. The effects of the enzyme on various yeast enzymes were examined by measuring their inactivation. The enzyme inactivated 6-phosphogluconate dehydrogenase [EC 1.1.1.44] and uricase [EC 1.7.3.3], but not malate dehydrogenase [EC 1.1.1.37], alcohol dehydrogenase [EC 1.1.1.1], glutamate dehydrogenase [EC 1.4.1.3], glucose-6-phosphate dehydrogenase [EC 1.1.1.49] or hexokinase [EC 2.7.1.1].