Glycation of human lens proteins: preferential glycation of alpha A subunits.
Glycation of crystallins and high molecular weight (HMW) aggregates was followed during aging (16-85 years) and in diabetes (44 and 70 years old). Lens soluble and insoluble fractions were reduced with [3H]NaBH4 and separated by molecular sieve HPLC. The protein content in each HPLC peak was measured by the Lowry method. The tritium incorporation, expressed as cpm mg-1 protein, was taken as a measure of early glycation and specific non-tryptophan fluorescence (Ex: 370 nm; Em: 440 nm), expressed as relative fluorescence U mg-1 protein, was taken as a measure of advanced glycation. The youngest lenses analysed were 16 and 17 years old and these provided the baseline values. The results showed that during aging there was about a three-fold increase in tritium incorporation and fluorescence of alpha-crystallin, while the increases in beta and gamma were only two-fold from the levels seen in 16- and 17-year-old lenses. On the other hand, both the soluble and insoluble HMW aggregate fractions showed up to five-fold increase in tritium incorporation during aging. The fluorescence was about two-fold higher in the insoluble HMW aggregates as compared to the soluble HMW aggregates in 16- and 17-year-old lenses and both showed an increase of about three-fold during aging. Diabetes resulted in an approximately 10-50% increase in tritium incorporation and non-tryptophan fluorescence of various crystallins and HMW aggregates.(ABSTRACT TRUNCATED AT 250 WORDS)
Swamy
M S
MS
Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912-2100.
Abraham
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A
Abraham
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EC
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D002851:Chromatography, High Pressure Liquid; D003459:Crystallins / Q000737:chemistry / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006031:Glycosylation; D006801:Humans; D007908:Lens, Crystalline / Q000737:chemistry / Q000378:metabolism*; D008875:Middle Aged; D011134:Polysaccharides / Q000032:analysis / Q000378:metabolism*
D003459:Crystallins; D011134:Polysaccharides