Abstract: A heat-stable nuclease found in Y. enterocolitica subsp. Palearctica, named Nucyep, is active in broad spectrum conditions. The gene for Nucyep was sequenced in a strain Y. enterocolitica subsp. palearctica, cloned, and expressed in E. coli, and then purified and characterized. The molecular weight of this enzyme is about 30 to 32 kDa. The translation product, Nucyep1, is biologically active. The purified Nucyep1 exhibits non-specific nuclease activity, being able to degrade various nucleic acids, including RNA, single-stranded DNA (ssDNA) and linear or circular double-stranded DNA (dsDNA). This enzyme is active in a wide range of temperatures, from 0 to 100° C. The enzyme is active in a wide range of pH values from 3.6 to 9.9, and keeps greater than 75% of the activity at pH 7.24. This enterobacterial nuclease has unique levels of intrinsic resistance to heat, and is active under a large spectrum of conditions.