Phosphatase activity of the blue-green alga (cyanobacterium) Nostoc commune UTEX 584

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Abstract
Nostoc commune UTEX 584 observed to grow on a range of organic phosphates, indicating the possession of phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activities, but it was unable to utilize phytic acid. The use of .rho.-nitrophenyl phosphate (.rho.NPP) as substrate showed the presence of cell-bound and extracellular PMEase. Cell-bound PMEase and PDEase were detected during growth in batch cultures, when the mean cellular phosphate content fell to 0.76% algal dry weight. Use of bis-.rho.-nitrophenyl phosphate (bis-.rho.NPP) showed that cell-bound PDEase activity (measured as .rho.-nitrophenol released) was about half that of PMEase, but that no extracellular PDEase activity was present. PMEase and PDEase activities both decreased when the cellular phosphate content fell below 0.3%. The optimum temperatures for PMEase and PDEase activity at pH 7.6 were 32.degree. C and 42.degree. C, respectively; the optima were lower when the assay was performed at pH 10.3. The pH optima for PMEase and PDEase differed slightly (7.0 vs. 7.8), but the influence of other ions tested (phosphate, Na, K, Mg, Ca, Zn) was similar for each activity. The most clear-cut effects were inhibition by phosphate and Zn, and enhanced activity when the Ca concentration was increased from 1 to 10 mM. Studies on the influence of desiccation showed that both PMEase and PDEase activities were regained rapidly on re-wetting, with no measurable lag before steady-state rates were measured. PMEase activity returned to the value reported before dessication, but PDEase showed a 40% increase in rat following desiccation and re-wetting.