Purification and characterization of an extracellular, uracil specific ribonuclease from a Bizionia species isolated from the marine environment of the Sundarbans

The first ribonuclease (RNase) from the Cytophaga - Flavobacterium - Bacteroides phylum, dominant in the marine environment, and also from the first Bizionia species isolated from the tropics was purified and characterized. Extracellular RNase production occurred when the culture medium contained 5 - 7% (w/v) NaCl The 53.0 kDa enzyme was purified 29 folds with a recovery of 4% and specific activity of 630 unit/mg protein. The pH and temperature optima are 6.5 and 35 degrees C, respectively and the enzyme retains more than half of its activity (relative to optima( assay conditions) after 1 h pre-incubation separately with 5% (w/v) NaCl or from pH 5.0 to 8.5 or at 50 degrees C. Dithiothreitol and beta-mercaptoethanol do not inhibit whereas human placental RNase inhibitor protein halves the RNase activity. While Mg2+, Ba2+ and Ca2+ enhanced the enzyme activity, Fe2+, CU2+ and Hg2+ inactivated it. This RNase degrades uracil containing nucleic acids only. Our isolate could be a novel renewable source of deoxyribonuclease (DNase) -free RNase enzyme. (c) 2006 Elsevier GmbH. All rights reserved.