Open AccessIdentification of a new derepressible phosphatase in Chlamydomonas reinhardtii
Author(s) -
Bachir Fatima,
Loppes Roland
Publication year - 1997
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1997.tb10328.x
Subject(s) - chlamydomonas reinhardtii , phosphatase , mutant , alkaline phosphatase , acid phosphatase , biochemistry , chlamydomonas , enzyme , biology , microbiology and biotechnology , chemistry , gene
In the unicellular green alga Chlamydomonas reinhardtii there are two highly expressed derepressible phosphatases (DN and DA). Mutants altered in DN phosphatase (phoN) or/and DA phosphatase (phoA) activities are available. From the double mutant phoN6 phoA4 showing only some residual phosphatase activity at alkaline pH, a mutant ( phoN6 phoA4 R18 ) displaying higher phosphatase activity at pH 9.5 was isolated. Comparative study of the phosphatase produced by the two strains revealed the enzymes to have very similar properties ( K m for α‐naphthylphosphate, thermosensitivity, pH dependence). In addition, a 58 kDa polypeptide present in the wild‐type strain and previously described as a component of a derepressible phosphatase, was shown to be more abundant in phoN6 phoA4 R18 . These results provide strong evidence that the residual enzyme in phoN6 phoA4 corresponds to a minor hitherto unknown phosphatase (DM) which is present in minute amounts in all P i ‐starved cells (including wild‐type where it is masked by the other phosphatases) and overproduced in phoN6 phoA4 R18 .