Low- and high-Km transport of dinitrophenyl glutathione in inside out vesicles from human erythrocytes.
Kinetic studies on the low- and high-Km transport systems for S-2,4-dinitrophenyl glutathione (DNP-SG) present in erythrocyte membranes were performed using inside-out plasma membrane vesicles. The high-affinity system showed a Km of 3.9 microM a Vmax of 6.3 nmol/mg protein per h, and the low-affinity system a Km of 1.6 mM and a Vmax of 131 nmol/mg protein per h. Both uptake components were inhibited by fluoride, vanadate, p-chloromercuribenzoate (pCMB) and bis(4-nitrophenyl)dithio-3,3'-dicarboxylate (DTNB). The low-Km uptake process was less sensitive to the inhibitory action of DTNB as compared to the high-Km process. N-Ethylmaleimide (1 mM) inhibited the high-Km process only. The high-affinity uptake of DNP-SG was competitively inhibited by GSSG (Ki = 88 microM). Vice versa, DNP-SG inhibited competitively the low-Km component of GSSG uptake (Ki = 3.3 microM). The high-Km DNP-SG uptake system was not inhibited by GSSG. The existence of a common high-affinity transporter for DNP-SG and GSSG in erythrocytes is suggested.
Akerboom
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TP
Institut für Physiologische Chemie I, Universität Düsseldorf, Germany.
Bartosz
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G
Sies
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D001692:Biological Transport; D002729:Chloromercuribenzoates / Q000494:pharmacology; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D005459:Fluorides / Q000494:pharmacology; D005978:Glutathione / Q000031:analogs & derivatives* / Q000378:metabolism; D019803:Glutathione Disulfide; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D013379:Substrate Specificity; D014638:Vanadates / Q000494:pharmacology
D002729:Chloromercuribenzoates; C030190:S-(2,4-dinitrophenyl)glutathione; D014638:Vanadates; D004228:Dithionitrobenzoic Acid; D005978:Glutathione; D005033:Ethylmaleimide; D005459:Fluorides; D019803:Glutathione Disulfide