Hyperalkaline and thermostable phosphatase in Thermus thermophilus

The phosphatases existing in the extreme thermophilic bacterium Thermus the rmophilus have been studied. Utilizing ion exchange, hydrophobic, pseudoaff inity, and affinity chromatography, a number of distinct phosphatase activi ties were identified. At least four phosphatases, with optimum pH ranging b etween 5.0 and 11.5, were assayed with p-nitrophenylphosphate, and two with optimum pH between 7.0 and 11.0, with P-32-casein as substrate. The author s have focused on the hyperalkaline phosphatase and have tried to purify an d characterize it. This hyperalkaline phosphatase reaches a maximal level a t the stationary phase of the growth, and is co-purified with alkaline phos phatase with optimum pH of 10.2. The enzymes present a relative mol wt of 6 5 and 58 kDa, respectively, as judged by SDS-PAGE and Sephadex G-150 column , and possess similar properties, indicating that they are isoforms. These enzymes barely function in the presence of tartrate, and are inhibited by E DTA, pyrophosphate, and molybdate. Among the metals tested, Hg2+ appeared a s the strongest inhibitor of the hyperalkaline phosphatase. The two enzymes are thermostable and, upon treatment at 90 degrees C for 10 min, 75% of th eir activity remains. The physiological role and function of these phosphat ases need further investigation.