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The bacterial-like lactate shuttle components from heterotrophic Euglena gracilis.
- Source :
-
Biochimica et biophysica acta [Biochim Biophys Acta] 2005 Sep 05; Vol. 1709 (2), pp. 181-90. - Publication Year :
- 2005
-
Abstract
- The structural and kinetic analyses of the components of the lactate shuttle from heterotrophic Euglena gracilis were carried out. Mitochondrial membrane-bound, NAD(+)-independent d-lactate dehydrogenase (d-iLDH) was purified by solubilization with CHAPS and heat treatment. The active enzyme was a 62-kDa monomer containing non-covalently bound FAD as cofactor. d-iLDH was specific for d-lactate and it was able to reduce quinones of different redox potential values. Oxalate and l-lactate were mixed-type inhibitors of d-iLDH. Mitochondrial l-iLDH also catalyzed the reduction of quinones, but it was inactivated during the extraction with detergents. Both l-iLDH and d-iLDH were inhibited by the specific flavoprotein-inhibitor diphenyleneiodonium, suggesting that l-iLDH was also a flavoprotein. Affinity chromatography revealed that the E. gracilis cytosolic fraction contained two types of NAD(+)-dependent LDH specific for the generation of d- and l-lactate (d-nLDH and l-nLDH, respectively). These two enzymes were tetramers of 126-132 kDa and showed an ordered bi-bi kinetic mechanism. Kinetic properties were different in both enzymes. Pyruvate reduction by d-nLDH was inhibited by its two products; the d-lactate oxidation was 40-fold lower than forward reaction. l-lactate oxidation by l-nLDH was not detected, whereas pyruvate reduction was activated by fructose-1, 6-bisphosphate, K(+) or NH(4)(+). Interestingly, membrane-bound l- and d-lactate dehydrogenases with quinone reductase activity have been only detected in bacteria, whereas the activity of soluble d-nLDH has been identified in bacteria and some yeast. Also, FBP-activated l-nLDH has been found solely in lactic bacteria. Based on their similar kinetic and structural characteristics, a possible common origin among bacterial and E. gracilis lactic dehydrogenase enzymes is discussed.
- Subjects :
- Animals
Bacterial Proteins chemistry
Energy Metabolism
Evolution, Molecular
Kinetics
Lactate Dehydrogenases isolation & purification
Lactate Dehydrogenases metabolism
Lactic Acid chemistry
Lactic Acid metabolism
Molecular Structure
Euglena gracilis enzymology
Lactate Dehydrogenases chemistry
Subjects
Details
- Language :
- English
- ISSN :
- 0006-3002
- Volume :
- 1709
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Biochimica et biophysica acta
- Publication Type :
- Academic Journal
- Accession number :
- 16112076
- Full Text :
- https://doi.org/10.1016/j.bbabio.2005.07.007