The purification and properties of a ribonuclease from squid

A ribonuclease in squid caecal fluid was partially purified and its properties studied. The enzyme is optimally active at pH 5.3 and is relatively stable to heating and treatment with acid. It was purified approximately 300-fold by heat treatment and salt gradient elution from a carboxymethylcellulose column. The purified enzyme was free of deoxyribonuclease, phosphatase, and phosphodiesterase activity. Specificity studies indicated that the squid enzyme could hydrolyze either purine or pyrimidine diester bonds. It also slowly split, 2′,3′-cyclic adenosine phosphate but did not hydrolyze 2′,3′-cyclic pyrimidine phosphates.