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Metal‐catalyzed inactivation of bovine glucose‐6‐phosphate dehydrogenase — role of thiols
Author(s) -
Maier Konrad L.,
Hinze Helga,
Meyer Barbara,
Lenz Anke-Gabriele
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(96)01054-x
Subject(s) - chemistry , glutathione , chelation , cysteine , enzyme , biochemistry , dehydrogenase , thiol , glucose 6 phosphate dehydrogenase , superoxide dismutase , catalysis , phosphate , inorganic chemistry
The role of thiols as oxidant scavengers during inactivation of bovine glucose‐6‐phosphate dehydrogenase by metal‐catalyzed oxidation systems has been studied in vitro. Partial inactivation of the enzyme was achieved by the metal‐catalyzed oxidation systems Fe(II)/H 2 O 2 /EDTA or Fe(II)/ H 2 O 2 /ADP under specific conditions. When EDTA as chelator was present in the oxidation system, both cysteine and N ‐acetylcysteine at low concentrations (0.1 – 1 mM) drastically enhanced inactivation, while cysteinyl‐glycine and glutathione did not. The thiol‐mediated inactivation was inhibitable by superoxide dismutase. Depletion of enzyme activity by cysteine was paralleled by an increase of the carbonyl content, which indicates oxidative injury. However, when EDTA as chelator was replaced by the natural chelator ADP, all thiols studied acted as antioxidants. It is therefore concluded that the nature of the chelator as a constituent of the metal‐catalyzed oxidation systems determines whether the antioxidative function of some thiols is shifted to a prooxidative function against glucose‐6‐phosphate dehydrogenase.