Kinetic parameters of superhelical DNA cleavage by endonuclease S1

Major kinetic parameters of endonuclease S1 were determined on superhelical bacteriophage PM2 DNA and on relaxed nicked circular PM2 DNA. At 37 degrees and 0,25 M NaCl, the Michaelis constants were respectively 1.7 . 10(-8) M and 1 . 10(-9) M, and catalytic constants were respectively 0.36 sec-1 and 1.2 . 10(-2) sec-1. The inhibition of the enzyme reaction by its product was detected.