Nonenzymatic glycation of human lens crystallin. Effect of aging and diabetes mellitus.
We have examined the nonenzymatic glycation of human lens crystallin, an extremely long-lived protein, from 16 normal human ocular lenses 0.2-99 yr of age, and from 11 diabetic lenses 52-82-yr-old. The glucitol-lysine (Glc-Lys) content of soluble and insoluble crystallin was determined after reduction with H-borohydride followed by acid hydrolysis, boronic acid affinity chromatography, and high pressure cation exchange chromatography. Normal lens crystallin, soluble and insoluble, had 0.028 +/- 0.011 nanomoles Glc-Lys per nanomole crystallin monomer. Soluble and insoluble crystallins had equivalent levels of glycation. The content of Glc-Lys in normal lens crystallin increased with age in a linear fashion. Thus, the nonenzymatic glycation of nondiabetic lens crystallin may be regarded as a biological clock. The diabetic lens crystallin samples (n = 11) had a higher content of Glc-Lys (0.070 +/- 0.034 nmol/nmol monomer). Over an age range comparable to that of the control samples, the diabetic crystallin samples contained about twice as much Glc-Lys. The Glc-Lys content of the diabetic lens crystallin samples did not increase with lens age.
D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D003459:Crystallins / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007223:Infant; D007908:Lens, Crystalline / Q000378:metabolism*; D008239:Lysine; D008297:Male; D008875:Middle Aged; D012995:Solubility
D003459:Crystallins; D005947:Glucose; D008239:Lysine