The Membrane-bound L- and D-lactate dehydrogenase activities in mitochondria from Euglena gracilis.
Arch Biochem Biophys
; 390(2): 295-303, 2001 Jun 15.
Article
em En
| MEDLINE
| ID: mdl-11396932
The activity of the pyridine nucleotide-independent lactate dehydrogenase (iLDH) was characterized in mitochondria isolated from the protist Euglena gracilis. The dissociation constants for L- and D-lactate were similar, but the V(max) was higher with the d isomer. A ping-pong kinetic mechanism was displayed with 2,4-dichlorophenol-indolphenol (DCPIP), or coenzyme Q(1), reacting as the second substrate with the modified, reduced enzyme. Oxamate was a competitive inhibitor against both L- and D-lactate. Oxalate exerted a mixed-type inhibition regarding L- or D-lactate and also against DCPIP. The rate of L-lactate uptake was partially inhibited by mersalyl and lower than the rate of dehydrogenation, which was mersalyl-insensitive. These data suggested that the active site of L-iLDH was orientated toward the intermembrane space. The following observations indicated the existence of two stereo-specific iLDH enzymes in the inner membrane of Euglena mitochondria: a greater affinity of the D-iLDH for both inhibitors, D-iLDH thermo-stability at 70 degrees C and denaturation of L-iLDH, opposite signs in the enthalpy change for the association reaction of the isomers to the enzyme, differential solubilization of both activities with detergents, and different molecular mass.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Ácido Láctico
/
Lactato Desidrogenases
/
Euglena gracilis
/
L-Lactato Desidrogenase
/
Mitocôndrias
Limite:
Animals
Idioma:
En
Revista:
Arch Biochem Biophys
Ano de publicação:
2001
Tipo de documento:
Article
País de afiliação:
México
País de publicação:
Estados Unidos