Existence of an acid phosphatase and two molecular forms of an alkaline phosphatase in Aspergillus terricola [electronic resource].

Includes references.

Crude extracts of Aspergillus terricola contained acid and alkaline phosphatase activities. Optimum activity of the acid phosphatase, using phenyl phosphate as a substrate, was at pH 4 while that of the alkaline phosphatase was at pH 9. The rate of phosphate release at pH 9 was about two times that recorded at pH4. Fractionation of the proteins of the extracts using acetone precipitation followed by DEAE-Sephadex A-25 column chromatography revealed existence of two molecular forms of the alkaline phosphatase F I and F II. The purification folds achieved were about 106 and 215 for F I and F II respectively. Kinetic studies on these two isozymes showed that they have similar properties, such as, both were optimally active at pH 9-9.5 and at 40°C, both had broad substrate specificities as they were active towards glucose-6- phosphate, AMP, GMP, CMP, UMP, ADP, ATP, NAD and inorganic pyrophosphate. The two isozymes also exhibited similar heat inactivation kinetics and were completely inhibited by HgCI2, Na F and EDTA and activated by divalent cations such as Mg2+ . Mn2+ and Zn2+. Their substrate saturation kinetics were of the hyperbolic type and their apparent Km values were 1.3 and 1.1 x 10-3 M for F I and F II, respectively.

Summary in Arabic.

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