Inhibition of gamma-glutamylcysteine synthetase by cystamine: an approach to a therapy of 5-oxoprolinuria (pyroglutamic aciduria). |
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Authors: | O W Griffith A Larsson A Meister |
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Institution: | 1. Department of Biochemistry, Cornell University Medical College New York, N.Y. 10021, USA;2. Department of Pediatrics, St. Goran''s Children''s Hospital, Karolinska Institutet, 1121 Stockholm, Sweden |
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Abstract: | γ-Glutamylcysteine synthetase is strongly inhibited by cystamine; thus, 20 μM cystamine inhibited the activity by 50%. Inhibition is rapid and the inhibited enzyme is reactivated by dithiothreitol suggesting that cystamine reacts with an enzyme sulfhydryl group. Inhibition by cystamine is not prevented by MgATP, L-α-aminobutyrate, or L-glutamate suggesting that cystamine may not interact at the active site. Little or no inhibition was observed with N,N′-diacetyl cystamine, L-cystine, glutathione disulfide, 2-hydroxyethyl disulfide, and thioglycolate disulfide, whereas thiocholine disulfide produced moderate inhibition. Cystamine or an inhibitory analog of cystamine might be useful in the therapy of the disease 5-oxoprolinuria in which there is an overproduction of γ-glutamylcysteine. |
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