TRANS-SIALIDASE FROM TRYPANOSOMA-CRUZI EPIMASTIGOTES IS EXPRESSED AT the STATIONARY-PHASE and IS DIFFERENT FROM the ENZYME EXPRESSED in TRYPOMASTIGOTES
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1993-09-01
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We have studied the trans-sialidase from insect forms of Trypanosoma cruzi growing in axenic culture. Log phase epimastigotes expressed little or-no trans-sialidase activity, and were unable to incorporate exogenous sialic acid. Trans-sialidase started to be expressed at the late logarithmic phase, with specific activity increasing steadily as the culture reached the stationary phase. Trans-sialidase was purified from the late log phase epimastigote culture, which contained less than 2% of metacyclic forms, yielding a glycoprotein that migrated as a single 90-kDa band in sodium dodecyl sulfate gels. This enzyme features: (1) no reaction with antibodies against the peptide repeats present in the carboxy-terminal of trypomastigote trans-sialidase; (2) positive reaction with antibodies raised against a fragment of trypomastigote trans-sialidase that contains the active site; (3) similar kinetic properties and identical acceptor-donor specificity when compared to the trypomastigote enzyme; and (4) neuraminidase activity in the absence of acceptors. Upon differentiation into metacyclic forms, a trans-sialidase activity containing the carboxy-terminal repeats of the trypomastigote enzyme was released into the medium. These results suggest that epimastigotes express a developmentally regulated trans-sialidase that contains the same catalytic site but lacks the tandem amino acid repeats typical of trypomastigote trans-sialidase.
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Molecular and Biochemical Parasitology. Amsterdam: Elsevier B.V., v. 61, n. 1, p. 97-106, 1993.