Nonenzymatic glycosylation of bovine lens crystallins. Effect of aging.
We have investigated nonenzymatic glycosylation of crystallins from calf and mature bovine lenses (2-6 years old). The lens homogenates were treated with 200-fold molar excess of [3H]NaBH4 and the incorporation of radioactivity was determined. The extent of glycosylation was more precisely determined from the 6 N HCl hydrolysate of [3H]borohydride-treated proteins by analyzing the glucitol-lysine adduct on a high pressure cation exchange column. We found that the [3H]NaBH4 incorporation and the amount of glucitol-lysine detected increased with age, particularly in HM alpha crystallin, a high molecular weight aggregate which accumulates with aging. This age-related increase in nonenzymatic glycosylation was also demonstrated by a comparison of crystallins isolated from the cortex and nucleus of a single lens. Nonenzymatic glycosylation of lens crystallins exemplifies a new form of post-transitional modification of long-lived proteins in vivo.
D000375:Aging; D000818:Animals; D001894:Borohydrides; D002417:Cattle; D003459:Crystallins / Q000378:metabolism*; D006027:Glycosides / Q000378:metabolism*; D007908:Lens, Crystalline / Q000254:growth & development* / Q000378:metabolism; D046911:Macromolecular Substances; D008970:Molecular Weight; D010084:Oxidation-Reduction; D014316:Tritium
D001894:Borohydrides; D003459:Crystallins; D006027:Glycosides; D046911:Macromolecular Substances; D014316:Tritium