Pyruvate phosphate dikinase and pyrophosphate metabolism in the glycosome of Trypanosoma cruzi epimastigotes

被引:52
作者
Acosta, H
Dubourdieu, M
Quiñones, W
Cáceres, A
Bringaud, F
Concepción, JL
机构
[1] Univ Los Andes, Fac Ciencias, Ctr Ingn Genet, Unidad Bioquim Parasitos, Merida 5101, Venezuela
[2] Univ Bordeaux 2, CNRS, UMR 5016, Mol Parasitol Lab, F-33076 Bordeaux, France
来源
COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY | 2004年 / 138卷 / 04期
关键词
glycosome; pyruvate phosphate dikinase; PPDK; pyrophosphate; pyrophosphatase; Trypanosoma cruzi;
D O I
10.1016/j.cbpc.2004.04.017
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Pyruvate phosphate dikinase (PPDK) was recently reported in trypanosomatids, but its metabolic function is not yet known. The present work deals with the cellular localization and the function of the Trypanosoma cruzi enzyme. First, we show by digitonin titration and cell fractionation that the enzyme was essentially present in the glycosome matrix of the epimastigote form. Second, we address the issue of the direction of the reaction inside the glycosome for one part, our bibliographic survey evidenced a quite exergonic DeltaGdegrees' (at least -5.2 kcal/mol at neutral pH and physiologic ionic strength); for another part, no pyrophosphatase (PPase) could be detected in fractions corresponding to the glycosomes; therefore, glycosomal PPDK likely works in the direction of pyruvate production. Third, we address the issue of the origin of the glycosomal pyrophosphate (PPi): several synthetic pathways known to produce PPi are already considered to be glycosomal. This work also indicates the presence of an NADP(+)-dependent beta-oxidation of palmitoyl-CoA in the glycosome. Several pyruivate-consuming activities, in particular alanine dehydrogenase (ADH) and pyruvate carboxylase (PC), were detected in the glycosomal fraction. PPDK appears therefore as a central enzyme in the metabolism of the glycosome of T cruzi by providing a link between glycolysis, fatty acid oxidation and biosynthetic PPi-producing pathways. Indeed, PPDK seems to replace pyrophosphatase in its classical thermodynamic role of displacing the equilibrium of PPi-producing reactions, as well as in its role of eliminating the toxic PPi. (C) 2004 Elsevier Inc. All rights reserved.
引用
收藏
页码:347 / 356
页数:10
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