title: Isolation and study of mutants lacking a derepressible phosphatase in Chlamydomonas reinhardi.
abstract: In the green alga Chlamydomonas reinhardi, removal of inorganic phosphate from the culture medium results in the increase of phosphatase activity (derepression) in the wild-type (WT) strain as well as in a double mutant (P2Pa)) lacking the two main constitutive acid phosphatases. Following treatment of WT and P2Pa with N-methyl-N-nitro-N-nitrosoguanidine (MNNG), mutants were recovered which display very low phosphatase activities when grown in the absence of phosphate; as shown by electrophoresis, they lack one non-migrating phosphatase (PD mutants). This enzyme is active over a wide range of pH with an optimum at pH 7.5. The comparison of elctropherograms form WT and mutants grown on media with or without phosphate allowed us to provide a tentative definition of the pool of derepressible phosphatases in Chlamydomonas: in addition tothe neutral phosphatase lacking in PD mutants, Chlamydomonas produces two electrophoretic forms of alkaline phosphatase showing an optimal activity at pH 9.5.
mesh_terms: D000135:Acid Phosphatase / Q000096:biosynthesis; D002696:Chlamydomonas / Q000201:enzymology*; D003470:Culture Media; D004586:Electrophoresis; D004793:Enzyme Reactivators; D004794:Enzyme Repression; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D008769:Methylnitronitrosoguanidine; D009154:Mutation; D010710:Phosphates; D010744:Phosphoric Monoester Hydrolases / Q000096:biosynthesis*
chemical_list: D003470:Culture Media; D004793:Enzyme Reactivators; D010710:Phosphates; D008769:Methylnitronitrosoguanidine; D000135:Acid Phosphatase; D010744:Phosphoric Monoester Hydrolases