Identification of a heat-labile cellular nuclease in Staphylococcus aureus with properties similar to the extracellular nuclease (EC 3.1.4.7)

Besides the well-known heat-stable extracellular staphylococcal nuclease (EC 3.1.4.7) and cell surface bound nuclease, one more nuclease, which is heat-labile, has been identified and purified on phosphorylated cellulose column and characterized. Analyses by Sephadex G-75 gel chromatography indicates that the heat-labile cellular nuclease has molecular weight of about 16,000 similar to those of extracellular and cell-surface bound nucleases. Like the heat-stable nucleases, the heat-labile enzyme acts on both DNA and RNA, is more active on heat-denatured DNA, requires Ca²⁺ ions for activity and maximum catalytic activity is observed at pH 9.8–10 and at 45°C. The results suggest that the three enzymes have properties strikingly similar to one another and therefore may be related structurally.