PURIFICATION AND CHARACTERIZATION OF A DNASE GAMMA-LIKE ENDONUCLEASE FROM XENOPUS-LAEVIS LIVER

We recently found that two apoptotic DNase gamma-like endonucleases (3 6 and 38 kDa DNases) were present in Xenopus laevis larval and adult l iver cell nuclei and that their activities increased in metamorphic cl imax. Here, we purified the main DNase gamma-like endonuclease from Xe nopus laevis liver cell nuclei and characterized its physical and enzy matic properties in detail. The molecular mass of Xenopus liver nuclea r endonuclease was 38,000 daltons as determined by SDS-polyacrylamide gel electrophoresis, A native molecular mass of 35,000 was estimated b y gel filtration. The purified Xenopus liver endonuclease was a neutra l one and required both Ca2+ and Mg2+ for DNase activity. Unlike the m ammalian DNase gamma, the Ca2+/Mg2+ requirement could not be supplied by Mn2+, The inhibition profiles by aurintricarboxylic acid, sodium ci trate and divalent metal ions such as Co2+, Ni2+, Cu2+ and Zn2+ were s imilar to those of mammalian DNase gamma. These results suggest that t his endonuclease is a Xenopus laevis homolog of the mammalian apoptoti c endonuclease DNase gamma.