title: alpha-crystallin protects glucose 6-phosphate dehydrogenase against inactivation by malondialdehyde.
abstract: The present work investigates the effect of malondialdehyde (MDA) binding on the enzymic activity and on some structural properties of glucose 6-phosphate dehydrogenase (G6PD). We studied whether alpha-crystallin could protect the enzyme against MDA damage, and if so, by what mechanism. We also studied whether alpha-crystallin could renature G6PD denatured by MDA. alpha-Crystallin was prepared from bovine lenses by gel chromatography. MDA was freshly prepared and incubated with G6PD with or without alpha-crystallin. The results show that MDA reacted with G6PD non-enzymically causing inactivation at concentrations lower than those used previously on structural proteins. The modified enzyme became fluorescent. alpha-Crystallin, acting as a molecular chaperone, specifically protected the enzyme against inactivation by MDA. The enzyme was not reactivated by alpha-crystallin, but it was stabilised and protected against further denaturation. Complex formation between alpha-crystallin and the modified enzyme was demonstrated by immunoprecipitation. G6PD was very susceptible to MDA and we have shown for the first time that alpha-crystallin is able to protect the enzyme against this damage.
authors.affiliation: Nuffield Laboratory of Ophthalmology, University of Oxford, Walton Street, Oxford, UK.
authors.forename: E
authors.initials: E
authors.lastname: Ganea
authors.forename: J J
authors.initials: JJ
authors.lastname: Harding
mesh_terms: D000818:Animals; D002417:Cattle; D003459:Crystallins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D007908:Lens, Crystalline / Q000737:chemistry; D008315:Malondialdehyde / Q000378:metabolism / Q000494:pharmacology*; D018832:Molecular Chaperones / Q000378:metabolism; D011233:Precipitin Tests; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D013050:Spectrometry, Fluorescence
chemical_list: D003459:Crystallins; D018832:Molecular Chaperones; D008315:Malondialdehyde; D005954:Glucosephosphate Dehydrogenase