The historical unit definition for the 3′->5′ phosphodiesterase activity Nuclease P1 is as follows:
One unit is defined as the amount of enzyme required to liberate 1.0 μmole of acid soluble nucleotides from Torula Yeast total RNA per min at 37 °C in 1X Nuclease P1 Buffer.
This unit definition has been updated to be directly comparable to the 3′->5′ phosphodiesterase unit definition of Nuclease S1, such that the 3′->5′ phosphodiesterase activity unit definition of NEB’s Nuclease P1 is as follows:
