抄録
Properties of two DNA topoisomerases isolated from cauliflower inflorescence were further investigated using negatively supercoiled pBR322 DNA and its relaxed form as the substrates. It was revealed that the ATP-independent enzyme (topoisomerase-I) has the capacity to relax negatively or positively supercoiled DNA at the presence or absence of ATP. ATP-dependent enzyme (topoisomerase-II) also removes supercoils from negatively or positively supercoiled DNA at the presence of ATP, but its reaction products are found to have some different electrophoretic behaviour from the products by topoisomerase-I. Prepared substrates with a unique linking number was catalyzed with topoisomerase-I or -II, and electrophoresed, indicating that simultaneous breaking and rejoining of DNA strands by topoisomerase-I and topoisomerase-II take place on a single-strand of the duplex DNA and on doublestrands, respectively.
