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Reduction of extracellular dehydroascorbic acid by K562 cells
Author(s) -
Schweinzer Esther,
Mao Yulu,
Krajnik Paul,
Getoff Nicola,
Goldenberg Hans
Publication year - 1996
Publication title -
cell biochemistry and function
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.933
H-Index - 61
eISSN - 1099-0844
pISSN - 0263-6484
DOI - 10.1002/cbf.635
Subject(s) - dehydroascorbic acid , phloretin , extracellular , chemistry , intracellular , biochemistry , ascorbic acid , vitamin c , food science
K562 erythroleukaemic cells produced ascorbate when incubated with dehydroascorbic acid. The reduction depended on the number of cells and on the concentration of dehydroascorbic acid. The observed rate consists of a high affinity (apparent) K m 7 μ M , V max 3·25 pmol min −1 (10 6 cells) −1 and a low affinity component, which was non‐saturable up to 1 m M of DHA (rate increase of 0·1 pmol min −1 (10 6 cells) −1 (1 μ M of DHA −1 ). The rate was dependent on temperature and was stimulated by glucose and inhibited by phloretin, N ‐ethylmaleimide, parachloro‐mercuribenzoate and thenoyltrifluoroacetone. Although uptake of DHA proceeded at a higher rate than its extracellular reduction, the generation of extracellular ascorbate from DHA cannot be accounted for by intracellular reduction and the release of ascorbate, since the latter was not linear with time and had an initial rate of approximately 3 pmol min −1 (10 6 cells −1 ). At a concentration of DHA of 100 μ M this is 25 per cent of the observed reduction.