Biochemical studies on human corneal proteoglycans ?a comparison of normal and keratoconic eyes

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Abstract
Human corneas from normal (healthy) donors and patients with keratoconus were either metabolically labelled under organ culture conditions or investigated without preincubation. The sulfated proteoglycans were isolated from a 4M guanidinium chloride/2% Triton X 100 extract. Two predominant proteoglycans were obtained from normal cornea after digestion of total sulfated proteoglycans with chondroitin ABC-lyase or endo-β-galactosidase. One had an overall mass of 150 kDa, two dermatan sulfate chains (M r≈50 kDa) with an iduronic acid content of 24%–28% and, after chondroitin ABC-lyase digestion, a core protein of 48 kDa. The other proteoglycan had an overall mass of 110 kDa, one keratan sulfate chain of ≈60 kDa and, following endo-β-galactosidase (keratanase) digestion, a core protein of 46 kDa. Each proteoglycan population was further fractionated into two subpopulations by chromatography on concanavalin A-Sepharose. The dermatan sulfateand keratan sulfate-containing proteoglycans isolated from keratoconic and healthy cornea had comparableM r values and core proteins with identical molecular weights, but the ratio of dermatan sulfate/keratan sulfate proteoglycan was increased in keratoconic cornea and the keratan sulfate chains of two keratan sulfate proteoglycans from keratoconic cornea were considerably shorter (M r 44 and 33 kDa) than those from normal corneas.