Acta Biochimica et Biophysica 14. (1979)
1979 / 1-2. szám - Bánfalvi, G.-Csuzi, S.-Ohlbaum, A.-Antoni, F.: An Adenosine Triphosphate Dependent Deoxyribonuclease with Adenosine Triphosphatase Activity from Bacillus cereus
Acta Biochim. et Biophys. Acad. Sei. Hung. Vol. 14 ( 1—2), pp. 53—66 (1979) An Adenosine Triphosphate Dependent Deoxyribonuclease with Adenosine Triphosphatase Activity from Bacillus cereus G. Bánfalvi, S. Csuzi, A. Ohlbaum, F. Antoni Institute of Biochemistry I., Semmelweis University Medical School, Budapest, Hungary (Received June 19, 1978) An adenosine triphosphate-stimulated deoxyrib onuciease was purified to about 4200 fold from Bacillus cereus. The enzyme activity of the crude extract increased by a factor of about 5 after dialysis. One of the low molecular weight inhibitors of the crude extract was found to be inorganic phosphate. During enzyme purification two nucleases were identified. One of them was specific to denatured DNA and the other one degraded both denatured DNA and native DNA. The activity towards native DNA could be increased several times by ATP. Through all steps of purification the ATP-independent DNase always accompanied the ATP-dependent one and the ratio of their activity was found to be constant. The ATP-dependent DNase also possessed ATPase activity stimulated both by native and denatured DNA. The fact that ATPase was stimulated by DNA and went together with ATP-dependent DNase during purification suggests that these functions belong to the same enzyme complex. Maximal activity of ATPase had broader pH, Mg2+ and ATP concentration ranges than that of DNase. Cooperation of the two functions may be limited only to a narrow range of ATP concentration. Km for ATPase was 1.6x IO-4 M ATP. Introduction ATP-dependent DNase seems to be the enzyme involved in genetic recombination (Oishi, 1969; Greth, Chevallier, 1973; Clark, 1971; Vovis, Buttin, 1970). Hovewer, the mechanism of action of this so called ’’recombination enzyme“ of bacteria has not yet been elucidated in detail. Among the broad spectrum of activities towards different DNA substrates the enzyme possesses, in addition to the ATP-dependent DNase activity, a DNA-dependent ATPase activity as well (Vovis, Buttin, 1970; Anai et al., 1970; Nobrega et al., 1972; Smith, Friedman, 1972; Goldmark, Linn, 1972; Rosamond, Lunt, 1977). In enzymes purified to homogeneity (Doly, Anagnostopoulos, 1976) or to near homogeneity (Goldmark, Linn, 1972; Eichler, Lehman, 1977) the DNase and ATPase activities seemed to be tightly associated and therefore not to be separable. The ATP-dependent DNase reaction is accompanied by conformational changes of the DNA (Vovis, Buttin, 1970). The question arises whether or not the ATPase activity is stringently coupled with the degradation of DNA. There are indications that uncoupling of the DNase Acta Biochimica et Biophysica Academiae Scientiarum Hungaricae 14, 1979