EXTRACELLULAR RIBONUCLEASE FROM RHIZOPUS STOLONIFER - CHARACTERISTICSOF AN ATYPICAL - GUANYLIC ACID PREFERENTIAL - ENZYME FROM RIBONUCLEASE-T2 FAMILY

Citation
R. Chacko et V. Shankar, EXTRACELLULAR RIBONUCLEASE FROM RHIZOPUS STOLONIFER - CHARACTERISTICSOF AN ATYPICAL - GUANYLIC ACID PREFERENTIAL - ENZYME FROM RIBONUCLEASE-T2 FAMILY, Biochimica et biophysica acta (G). General subjects, 1379(2), 1998, pp. 264-272
Citations number
33
Categorie Soggetti
Biology,Biophysics
ISSN journal
03044165
Volume
1379
Issue
2
Year of publication
1998
Pages
264 - 272
Database
ISI
SICI code
0304-4165(1998)1379:2<264:ERFRS->2.0.ZU;2-2
Abstract
An extracellular ribonuclease from Rhizopus stolonifer (designated as RNase Rs) was purified to homogeneity by chromatography on DEAE-cellul ose followed by CM-cellulose. The Mr of the purified enzyme determined by gel filtration and SDS-PAGE is 25 000 and 28 200, respectively. RN ase Rs is a glycoprotein and contains 10.5% neutral sugar. It is an ac idic protein with a pI of 5.0 and has a blocked N-terminus. The optimu m pH and temperature are 5.5 and 45 degrees C, respectively. RNase Rs shows high stability between pH 6.0-10.0. Divalent cations like Zn2+, Hg2+ and Cu2+ inhibit the enzyme activity whereas, mononucleotides doe s not have any significant effect. The enzyme cleaves RNA to 3'-mono-n ucleotides via 2',3'-cyclic nucleotides, with preferential liberation of 2',3'-cyclic GMP, suggesting that RNase Rs is a guanylic acid prefe rential cyclizing RNase. Moreover, cyclic nucleotides generated are hi ghly resistant to further hydrolysis. (C) 1998 Elsevier Science B.V.