Identification and characterization of the acid phosphatase from Francisella tularensis and its potential role in pathogenesis
Reilly, Thomas James
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Permalink
https://hdl.handle.net/2142/22043
Description
Title
Identification and characterization of the acid phosphatase from Francisella tularensis and its potential role in pathogenesis
Author(s)
Reilly, Thomas James
Issue Date
1994
Doctoral Committee Chair(s)
Kuhlenschmidt, Mark S.
Department of Study
Pathobiology
Discipline
Pathobiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Microbiology
Agriculture, Animal Pathology
Biology, Veterinary Science
Language
eng
Abstract
Successful intracellular pathogens resist or prevent the formation of antimicrobial substances produced by professional phagocytes including, toxic oxygen intermediates of the respiratory burst. Purified acid phosphatases (ACP) from Leishmania donovani and Legionella micdadei have been shown to cause the dose dependent suppression of the respiratory burst (Remaley et al., 1984 and Saha et al., 1985). Depression of the respiratory burst by phosphatase-catalyzed dephosphorylation of phosphatidylinositol 4,5-bisphosphate and inositol 1,4,5-trisphosphate is believed to play an important role in the intracellular survival of these pathogens. Results from this study show that the intracellular pathogen, F. tularensis (Ft) produces a respiratory burst-inhibiting acid phosphatase. The acid phosphatase appears to be identical in three strains tested. Like many microbial acid phosphatases, FtACP has been localized to the periplasmic space of the organism. FtACP has the following properties: molecular mass $\sim$56 kDa, pH optimum of 6.0 for five different substrates, isoelectric point of 9.2, broad substrate specificity including. The enzyme was inhibited by molybdate, vanadate, and mercury but was resistant to scL-(+) tartrate, fluoride, chelators of divalent cations, and okadaic acid. FtACP possesses protein tyrosyl phosphatase activity when incubated in the presence of the monophosphorylated peptide p60$\sp{\rm src}$. Another unusual property of this bacterial phosphatase is that it appears to possess covalently associated carbohydrates tentatively identified as glucose, mannose, and galactose. Like other burst inhibiting acid phosphatases, this enzyme caused the dose dependent suppression of fMLP stimulated neutrophils and displayed maximum effects on the respiratory burst after a 15 minute pre-incubation period. Unlike other respiratory burst-inhibiting acid phosphatases, FtACP inhibited the respiratory burst of PMA stimulated neutrophils. Preliminary evidence also suggests FtACP may inhibit the expansion of Con A stimulated T cells. These data are consistent with the hypothesis that FtACP plays a role in the survival and virulence of this pathogen. Another interesting aspect of this study is that FtACP cannot equivocally be classified into any of the existing classes of acid phosphatases. This conclusion may be a consequence of the dual role for this enzyme: intracellular survival and axenic growth.
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