STREPTOCOCCAL NUCLEASES

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Abstract
Strepto-coccal DNase C is more resistant to heat inactivation than the A or B enzyme. The DNases A and C are indifferent to the bacterial RNA inhibitor whereas the B enzyme is markedly inhibited. Prolonged digestion with relatively large amounts of DNase B results in chemical and biological destruction of the inhibitor. RNase as well as DNase activity is associated with the B enzyme. Both activities require divalent cations, and both are inhibited by bacterial RNA. The ratios of the 2 activities are constant in various preparations and after partial heat inactivation. Mutual inhibition of the 2 activities can be demonstrated in mixed substrate system, indicating that the B enzyme is a single nuclease which can attack both DNA and RNAacids.