ISOFORMS OF SERRATIA-MARCESCENS NUCLEASE - COMPARATIVE-ANALYSIS OF SUBSTRATE-SPECIFICITY

Comparative analysis of the specificity of Serratia marcescens nucleas e isoforms has been carried out. Mononucleotides separated by anion-ex change chromatography in the presence of 7 M urea from partially hydro lyzed RNA with nucleases Sm1 and Sm2 were identified by reverse-phase HPLC. Both enzymes were found to split phoshodiester bonds at nearly a ll nucleic acid bases. However, nuclease Sm1 demonstrated preferential cleavage of phosphodiester bonds near uracil and nuclease Sm2 near gu anine. A possible role of the N-terminal tripeptide fragment in the nu clease mechanism is discussed.