A P subtype restriction enzyme that recognizes the double-stranded unmethylated sequence 5'-GATC-3' and cleaves before G-1. Endonucleolytic cleavage of DNA to give specific double-stranded fragments with terminal 5'-phosphates. The LlaDCHI restriction system has two different methylases. Genes encoded on plasmid pSQR700 confer strong resistance to the three most common lactococcal phage species (936, c2, and P335). Its presence is probably one reason for the strong bacteriophage resistance shown by strain DCH-4 over the years. Belongs to the DpnII type II restriction endonuclease family.