Aspartic acid racemization in heavy molecular weight crystallins and water insoluble protein from normal human lenses and cataracts.

Abstract

High D/L aspartic acid ratios were observed in heavy MW aggregates and in water-insoluble protein extracted from whole lenses and nuclear and cortical regions. Purified .alpha.-.beta.- and .gamma.-crystallins had low D/L ratios. Fractionation of urea-solubilized material from the water-insoluble protein yielded 4 MW classes of proteins. Fractions representing crosslinked material or apparently degraded products had high D/L ratios. Racemization within lens proteins may contribute to formation of the water-insoluble fraction seen in aging lenses and cataracts.