Immunocytochemical localization of carbonic anhydrase isozyme III in equine thymus

Sections of equine thymus were examined for the presence of carbonic anhydrase (CA) isozymes by an immunohistochemical method. Carbonic anhydrase III, a major enzyme of skeletal muscle, was localized in some of the epithelial-reticular cells of the equine thymus. This finding suggests the presence of a new type of cell in the thymic cortex. The concentration of CA-III in the thymus was 17 micrograms/g wet tissue. CA-I and CA-II were not found in equine thymus.     

Calpain II-like proteinase of scallop (Patinopecten yessoensis) striated adductor muscle.

1. A Ca(2+)-dependent cysteine proteinase was purified from scallop striated adductor muscle by ammonium sulfate fractionation and column chromatography on DEAE-cellulose and Sephacryl S-300. 2. The enzyme is of Mr approximately 200,000, composed of two Mr 100,000 subunits. 3. The enzyme is a cysteine proteinase with optimum activity at pH 6.8 and about 18 degrees C. In addition, it requires 1.7 mM Ca2+ for half-maximal activity and more than 10 mM Ca2+ for maximal activity. Thus the enzyme can be classified as calpain II.