INVESTIGADORES
CYMERYNG Cora Beatriz
artículos
Título:
Phosphoenolpyruvte carboxykinase from Trypanosoma cruzi. Purification and physicochemical and kinetic properties.
Autor/es:
CYMERYNG, CORA BEATRIZ; CAZZULO, JUAN JOSÉ; CANNATA, JOAQUÍN JB
Revista:
MOLECULAR AND BIOCHEMICAL PARASITOLOGY
Editorial:
Elsevier
Referencias:
Año: 1995 vol. 73 p. 91 - 101
ISSN:
0166-6851
Resumen:
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Phosphoenolpyruvate carboxykinae (PEPCK) has been purified to homogeneity from epimastigotes of the Tul 0 strain of Trypanosoma cruzi. The physicochemical parameters determined allowed the calculation of an average molecular mass of 120 kDa; the subunit molecular mass, about 61 kDa, is in good agreement with the value of 58.6 kDa recently determined from the sequence by Sommer et al. (FEBS Lett. 359, 1994, 125-129). The PEPCK from T. cruzi presented, in addition to its molecular mass, typical properties of other ATP-linked PEPCKs, namely strict specificity for ADP in the carboxylation reaction and lower specificity in the decarboxylation and exchange reactions, and synergistic activation by CdCl2 or MgCl2 when added in addition to MnCl2. The enzyme presented hysteretic behavior, shown by a lag period in the carboxylation reaction, which was affected by dilution and preincubation. The decarboxylation reaction catalyzed by the T. cruzi PEPCK was not inhibited by excess of ATP_Mn. The apparent Km values for the carboxylation reaction, including the low value for PEP (0.035 mM) are compatible with an important role of PEPCK, as suggested by previous NMR experiments, on the CO2 fixation in vivo which leads to succinate excretion during aerobic fermentation of glucose.
