title: Diminished susceptibility to proteolysis after protein modification by the lipid peroxidation product malondialdehyde: inhibitory role for crosslinked and noncrosslinked adducted proteins.
abstract: The lipid peroxidation product malondialdehyde forms adducts with proteins that are detected during routine assays for protein carbonylation. To test whether this damage alters the susceptibility of a protein to proteolysis, we treated bovine serum albumin with various concentrations of malondialdehyde and examined its susceptibility to digestion by alpha-chymotrypsin. In keeping with findings concerning the consequences of protein damage by other carbonyl products of lipid peroxidation, we found that malondialdehyde-modified protein was resistant to proteolysis. Since significant protein crosslinking occurred during modification with malondialdehyde, we investigated the possibility that crosslinked proteins were acting as proteolytic inhibitors. Malondialdehyde-modified proteins were resolved into crosslinked and noncrosslinked forms and the effectiveness of both species as proteolytic antagonists was examined. While both forms of malondialdehyde-adducted proteins were more potent proteolytic inhibitors than unmodified albumin, there were no significant differences in inhibitory potency between crosslinked and noncrosslinked proteins. Our findings suggest that malondialdehyde-modification produces protease-resistant proteins without an obligatory role for crosslinking.
authors.affiliation: Department of Clinical and Experimental Pharmacology, University of Adelaide, Australia. pburcham@medicine.adelaide.edu.au
authors.forename: P C
authors.initials: PC
authors.lastname: Burcham
authors.forename: Y T
authors.initials: YT
authors.lastname: Kuhan
mesh_terms: D000818:Animals; D002417:Cattle; D002918:Chymotrypsin / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000737:chemistry; D010450:Endopeptidases / Q000378:metabolism*; D006868:Hydrolysis; D008054:Lipid Peroxides / Q000378:metabolism*; D008315:Malondialdehyde / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000378:metabolism
chemical_list: D003432:Cross-Linking Reagents; D008054:Lipid Peroxides; D012710:Serum Albumin, Bovine; D008315:Malondialdehyde; D010450:Endopeptidases; D002918:Chymotrypsin