Properties of Phosphoglycolate Phosphatase from Chlamydomonas reinhardtii and Anacystis nidulans.
The levels of activity of 2-phosphoglycolate phosphatase in the green algae, Chlamydomonas reinhardtii and Chlorella vulgaris, were in the range of 37 to 60 micromoles per milligram chlorophyll per hour and in the blue-green algae, Anacystis nidulans and Anabaena variabilis were 204 to 310 micromoles per milligram chlorophyll per hour. The activity in each species was similar regardless of whether the algae were grown with air or 5% CO(2) in air. The enzyme purified 530-fold from Chlamydomonas was stable, had a broad pH optimum between 6 and 8.5, and was specific for the hydrolysis of P-glycolate with a K(m) of 23 micromolar. The enzyme purified 18-fold from Anacystis was labile, had a sharp pH optimum at 6.3, and was also specific for P-glycolate with a K(m) of 94 micromolar. The molecular weight of the enzyme from Chlamydomonas was estimated to be 92,000 by gel filtration.The phosphatase from both sources required a divalent cation for activity. The Chlamydomonas enzyme was most effectively activated by Co(2+), but was also activated by Mg(2+) (K(a) = 30 micromolar), Mn(2+), and Zn(2+). The Anacystis enzyme was most effectively activated by Mg(2+) (K(a) = 140 micromolar), and was also activated by Co(2+) and Mn(2+), but not by Zn(2+). Anions were also required for maximum activity of the enzyme from both sources. The Chlamydomonas enzyme was activated about 2- to 3-fold by chloride (K(a) = 140 micromolar), bromide, nitrate, bicarbonate (K(a) = 600 micromolar) and formate. The Anacystis enzyme was activated over 10-fold by chloride (K(a) = 870 micromolar), bromide, iodide, and nitrate, but was not activated by bicarbonate or formate.The properties of the algal enzymes were similar to those previously reported for higher plants. The levels and kinetic properties of the enzyme seemed sufficient to account for the flux through the glycolate pathway that occurs in these algae. The phosphatase was not associated with the ribulose 1,5-bisphosphate carboxylase/oxygenase responsible for P-glycolate formation in the carboxysomes of Anacystis.
Husic
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Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824.
Tolbert
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