Ribonuclease A (RNASEA) is a member of the pancreatic-type of secretory ribonucleases, a subset of the ribonuclease A superfamily. RNASEA cleaves RNA on the 3' side of pyrimidine nucleotides. The protein acts to degrade ds-RNA over ss-RNA. The activity of recombinant human RNASEA measured by cleaving yeast RNA. One unit of the enzyme causes an increase in absorbance of 0.001 at 260 nm in 15 min when yeast RNA is hydrolyzed at 50°C and pH 5.0. Pipette 50ulof respective recombinant human RNASEA dilution into 100ul 0.1M sodium acetate buffer, pH 5.0, then add 150ul of 0.15mg/ml yeast RNA. The blank tube use 50ul ultrapure water instead of enzyme dilution. All the all tubes Incubate at 50°C for 15 minutes. Read A260 versus blank.