A Biological Assay for Ribonuclease with Sub-millimicrogram Sensitivity

Abstract

Infectious ribonucleic acid (RNA) isolated from foot-and-mouth disease virus was exposed to known concentrations of ribonuclease (RNase), and the resulting loss in RNA activity was measured by plaque assay in calf-kidney cultures. The enzyme was shown to be hydrolyzing its substrate and not merely forming an inactive complex with it. Concentrations of RNase as low as 0.1 milli-[mu]g per ml were readily detected. The RNase content of sera of several animals and of man ranged from 0.02 to 0.12 [mu]g/ml, while guinea pig serum contained 20 to 30 times as much. It is suggested that other viral RNA could be used as the enzyme substrates, and that a comparable ultrasensitive assay for deoxyribonuclease could be devised using a viral deoxyribonucleic acid substrate.