RNase activity was measured in a reaction mixture
containing 200µl citrate buffer (100mM, pH 3.5), 200µl yeast
RNA (substrate, 5mg/mlin the same buffer) 200µl of suitably
diluted enzyme solution. After incubation at 30°C for 15min,
the reaction was terminated by 200µl of 25% (v/v) perchloric
acid solution containing 0.75% (w/v) phosophotungstic acid
and 0.6% (w/v) bovine serum albumin. The undigested RNA
was precipitated by centrifugation at (10,000rpm for 10min)
and the acid soluble nucleotides were estimated
spectrophotometrically at 260nm (14). The amount of
acid-soluble ribonucleotides was calculated by assuming a
molar absorption coefficient of 10,600 L.mol-1 cm-1(4)
One unit of enzyme activity is defined as the activity to
release acid soluble oligonucleotides per minute to increase
one unit of A260 value in the reaction mixture.