Extracellular nucleases of Lysobacter enzymogenes: purification and characterization of a ribonuclease

Abstract

The ribonuclease of Lysobacter enzymogenes is one of two major extracellular nucleolytic enzymes produced by the organism. The enzyme was purified 560-fold and appeared to be free of contaminating proteins and interfering enzymes. The Lysobacter RNAase consists of one polypeptide chain with a molecular weight of 46 000 – 47 000. The enzyme was most active at pH 8.0–8.5 and in the presence of Mg2+. Approximately 45% of the maximum activity was obtained in the presence of Ca2+, whereas little or no activity was obtained in the presence of Mn2+ or without divalent metal ions. RNA, poly(A), and poly(C) served as substrates but DNA was not hydrolysed. High molecular weight RNA was degraded by the RNAase to short oligonucleotides with 5′-phosphate ends and there was no apparent base specificity.