The soluble adenosine triphosphatase of Thiobacillus ferrooxidans

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Abstract
Adenosine triphosphatase (ATPase) from Thiobacilhis ferrooxidans was purified 55-fold. Polyacrylamide gel electrophoresis of the most purified fraction showed only one major band; histochemical analysis showed that the ATPase activity was associated with this band. The pH optimum is 9–10. The enzyme hydrolyzed ATP stoichiometrically to ADP and inorganic phosphate, the Km for this substrate being 7.75 × 10−3 M. GTP and ITP are alternate substrates, the Km values for these being 6.71 × 10−3 M and 3.12 × 10−3 M, respectively. ADP is slightly hydrolyzed. Magnesium, manganese, and calcium can serve as cofactors; Km values for these are 2.0 × 10−3 M, 9.4 × 10−4 M, and 8.0 × 10−4 M, respectively. The enzyme activity was not activated by either sodium or potassium, but a combination of the two ions were inhibitory. Azide and p-hydroxymercuribenzoate strongly inhibited the enzyme activity, whereas cyanide, dinitrophenol, and N, N′-dicyclohexylcarbodiimide (DCCD) were without effect. The enzyme was cold labile at 0 °C, but was more stable at 18–24 °C.

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