New enzymes

We identified a bacterial strain, Paracoccus species 12, which produces a novel restriction endonuclease, named PecI. This enzyme recognizes the hexanucleotide palindromic DNA sequence 5’-TTA^TAA-3’ and cleaves it, as indicated by the arrow, generating blunt ends. Thus, PecI is a true isoschizomer of the restriction enzyme PsiI. A preparation of PecI restriction endonuclease at a concentration of 10,000 U/mL was obtained through a four-step chromatographic purification process. The optimal reaction conditions for the enzyme are SE-buffer 5 (Y) (33 mM Tris-acetate (pH 7.9), 10 mM Mg-acetate, 66 mM K-acetate, 1 mM DTT) and a temperature of 37oC.

We have discovered a bacterial strain Lysinibacillus manganicus An22 that produces the new prototype of restriction endonuclease named LmnI. This enzyme recognizes a nonpalindromic DNA sequence 5’-GCTCC-3’/3’-CGAGG-5’. The LmnI restriction endonuclease preparation with the concentration of 1000 units/ml was isolated using four chromatographic steps. It was shown that new enzyme cuts its recognition sequence forming 3’-protruding ends as indicated by the arrows: 5’-GCTCCN↓-3’/3’-CGAG↑GN-5’, and can be applied to a IIS type of restriction-modification systems.