STUDIES ON THERMOPHILIC SULFATE-REDUCING BACTERIA III. : Adenosine Triphosphate-sulfurylase of Clostridium nigrificans and Desulfovibrio desulfuricans1

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Akagi, J. M. (University of Kansas, Lawrence) and L. Leon Campbell. Studies on thermophilic sulfate-reducing bacteria. III. Adenosine triphosphate-sulfurylase of Clostridium nigrificans and Desulfovibrio desulfuricans. J. Bacteriol. 84:1194–1201. 1962.—Adenosine triphosphate (ATP)-sulfurylase, which catalyzes the formation of adenosine-5′-phosphosulfate (APS) from ATP and SO4=, has been purified from crude extracts of Clostridium nigrificans and Desulfovibrio desulfuricans by (NH4)2SO4 fractionation and triethylaminoethyl column chromatography. The enzyme from both sources operates over a broad pH range from 6.0 to 9.5. Below pH 6.0, activity decreases sharply, with no detectable activity at pH 5.0. Of the nucleotides tested (ATP and the triphosphates of deoxyadenosine, uridine, inosine, and guanosine), only ATP was acted upon by the enzyme from either source. The enzyme requires Mg++ for activity. Incubation of the enzyme from both organisms with ATP and S35O4= in the presence of helium resulted in the formation of an S35-labeled nucleotide whose electrophoretic mobility was identical to that of chemically prepared APS. When incubated with ATP and the group VI anions (CrO4, MoO4, WO4), the enzyme from both organisms formed an unstable intermediate, resulting in the accumulation of pyrophosphate. Thermal stability studies revealed that the ATP-sulfurylase of C. nigrificans was stable at higher temperatures than the enzyme obtained from D. desulfuricans. Exposure of the enzyme from C. nigrificans to 65 C for 2 hr gave virtually no decrease in activity. In contrast, the enzyme from D. desulfuricans was completely inactivated after 30 min at 55 C, after 3 min at 60 C, or after 1 min at 65 C.

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