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Phosphate or phosphite addition promotes the proteolytic turnover of phosphate‐starvation inducible tomato purple acid phosphatase isozymes
Author(s) -
Bozzo Gale G.,
Singh Vinay K.,
Plaxton William C.
Publication year - 2004
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2004.07.051
Subject(s) - extracellular , proteolysis , proteases , biochemistry , isozyme , serine , intracellular , biology , phosphate , phosphatase , acid phosphatase , microbiology and biotechnology , enzyme , pi , pmsf , chemistry
Within 48 h of the addition of 2.5 mM phosphate (HPO 4 2− , Pi) or phosphite (H 2 PO 3 − , Phi) to 8‐day‐old Pi‐starved (−Pi) tomato suspension cells: (i) secreted and intracellular purple acid phosphatase (PAP) activities decreased by about 12‐ and 6‐fold, respectively and (ii) immunoreactive PAP polypeptides either disappeared (secreted PAPs) or were substantially reduced (intracellular PAP). The degradation of both secreted PAP isozymes was correlated with the de novo synthesis of two extracellular serine proteases having M r s of 137 and 121 kDa. In vitro proteolysis of purified secreted tomato PAP isozymes occurred following their 24 h incubation with culture filtrate from Pi‐resupplied cells. The results indicate that Pi or Phi addition to −Pi tomato cells induces serine proteases that degrade Pi‐starvation inducible extracellular proteins.