Further investigations on the characterization of DNA topoisomerases isolated from cauliflower inflorescence.

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Abstract
Properties of 2 DNA topoisomerases isolated from cauliflower inflorescence were further investigated using negatively supercoiled pBR322 DNA and its relaxed form as the substrates. The ATP-independent enzyme (topoisomerase-I) has the capacity to relax negatively or positively supercoiled DNA in 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 have different electrophoretic behavior from the products by topoisomerase-I. Prepared substrates with unique linking numbers were 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 double-strands, respectively.