Cataract remains the major cause of blindness worldwide and a common complication of diabetes. Polyol accumulation in the lens is associated with cataract formation. Here me present evidence for a novel pathway for xylitol production in the lens involving glucuronate metabolism. Xylitol can be produced in rat and bovine lens from glucose, via the enzymes myo-inositol-oxygen oxidoreductase, D-glucuronate reductase, L-gulonate NAD+-3-oxidoreductase and L-iditol-NAD+-5-oxidoreductase, which have been found in the mammalian lens for the first time. Glucuronate reductase has been purified and was inhibited by thiol quenching reagents. UDP-glucuronyl transferase is also present in mammalian lenses; this enzyme may be an anti-toxic defense mechanism in the lens.
Goode, D., Lewis, M. E., & Crabbe, M. J. C. (1996). Accumulation of xylitol in the mammalian lens is related to glucuronate metabolism. FEBS Letters, 395(2–3), 174–178. https://doi.org/10.1016/0014-5793(96)01012-5