Folate transport by prawn hepatopancreas brush-border membrane vesicles.
The transport system of folic acid (Pte-Glu) by brush-border membrane vesicles (BBMV) isolated from prawn (Penaeus japonicus) hepatopancreas, was studied by measuring the uptake of Pte-Glu. This uptake was found to have two components, intravesicular transport and membrane binding. Membrane binding was not affected by the presence of a transmembrane pH-gradient at a short incubation period. However, a transmembrane pH-gradient increased membrane binding at 60 min. The transport of Pte-Glu appeared to be carrier-mediated, was stimulated by an inwardly proton gradient (pH 5.5 outside, 7.4 inside) and was unaffected by a sodium-gradient. The relationship between pH gradient-driven Pte-Glu uptake and medium Pte-Glu concentration followed saturating Michaelis-Menten kinetics. Eadie-Hofstee representation of the pH gradient-driven Pte-Glu uptake indicated a single transport system with a Km of 0.37 microM and Vmax of 1.06 pmol/mg protein/15 s. These findings indicate that BBMV isolated from prawn hepatopancreas possesses a Pte-Glu transport system similar to that described in mammalian intestine.
Blaya
J A
JA
Departamento de Fisiología y Biología Animal, Facultad de Farmacía, Sevilla, Spain.
Muriana
F J
FJ
Ruiz-Gutierrez
V
V
Vazquez
C M
CM
Bolufer
J
J
D000818:Animals; D001692:Biological Transport; D033364:Decapoda / Q000378:metabolism*; D004064:Digestive System / Q000378:metabolism*; D005492:Folic Acid / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008871:Microvilli / Q000378:metabolism
D005492:Folic Acid