title: Effects of inorganic and organic anions on the transport of phosphoenol-pyruvate across the erythrocyte membrane.
abstract: Phosphoenolpyruvate is transported across the erythrocyte membrane by a carrier-mediated transport system. The transport of phosphoenolpyruvate was competitively inhibited by inorganic phosphate (Ki = 24 mM) and pyridoxal 5-P (Ki = 0.2 mM), whereas the transport was non-competitively inhibited by L-(+)-lactate (Ki = 37 mM). Specific inhibitors for the inorganic anion transport system such as 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid strongly inhibited the phosphoenolpyruvate transport. Inhibitors for the monocarboxylate transport system, including p-chlormercuribenzoic acid and alpha-cyano-4-hydroxycinnamate, had less inhibitory effects on the phosphoenolpyruvate transport as high as 100 microM. The transport was inhibited irreversibly by treating erythrocytes with pryridoxal 5-P/NaBH4. Transport activities of phosphoenolopyruvate and inorganic phosphate in the treated cells were similarly inhibited depending on the pyridoxal 5-P concentration. The major integral membrane protein, Band 3, was preferentially labelled by treating erythrocytes with pyridoxal 5-P/[3H]-NaBH4. These results suggest that Band 3 mediates the transport of phosphenolopyrvate as well as inorganic phosphate.
mesh_terms: D000345:Affinity Labels / Q000494:pharmacology; D001457:Anion Exchange Protein 1, Erythrocyte; D000838:Anions; D001692:Biological Transport / Q000187:drug effects; D001798:Blood Proteins / Q000378:metabolism; D001894:Borohydrides / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D007773:Lactates / Q000494:pharmacology; D019344:Lactic Acid; D008565:Membrane Proteins / Q000097:blood / Q000302:isolation & purification; D010728:Phosphoenolpyruvate / Q000097:blood*; D011732:Pyridoxal Phosphate / Q000494:pharmacology; D012969:Sodium Fluoride / Q000494:pharmacology
chemical_list: D000345:Affinity Labels; D001457:Anion Exchange Protein 1, Erythrocyte; D000838:Anions; D001798:Blood Proteins; D001894:Borohydrides; D007773:Lactates; D008565:Membrane Proteins; D019344:Lactic Acid; D011732:Pyridoxal Phosphate; D010728:Phosphoenolpyruvate; C025364:sodium borohydride; D012969:Sodium Fluoride