Immunochemical detection of oxalate monoalkylamide, an ascorbate-derived Maillard reaction product in the human lens

Carbohydrates with reactive aldehyde and ketone groups can undergo Maillard reactions with proteins to form advanced glycation end products. Oxalate m onoalkylamide was identified as one of the advanced glycation end products formed from the Maillard reaction of ascorbate with proteins. In these expe riments, we have analyzed human lens proteins immunochemically for the pres ence of oxalate monoalkylamide, Oxalate monoalkylamide was absent in most o f the very young lenses but was present in old and cataractous lenses. The highest levels mere found in senile brunescent lenses. Incubation experimen ts using bovine lens proteins revealed that oxalate monoalkylamide could fo rm from the ascorbate degradation products, 2,3-diketogulonate and L-threos e. These data provide the first evidence for oxalate monoalkylamide in vivo and suggest that ascorbate degradation and its binding to proteins are enh anced during lens aging and cataract formation. (C) 1999 Federation of Euro pean Biochemical Societies.