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Lisa M. Bova, Andrew M. Wood, Joanne F. Jamie, Roger J. W. Truscott; UV Filter Compounds in Human Lenses: the Origin of 4-(2-Amino-3-hydroxyphenyl)-4-oxobutanoic Acid O-β-d-Glucoside. Invest. Ophthalmol. Vis. Sci. 1999;40(13):3237-3244.
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purpose. To investigate UV filter synthesis in the human lens, in particular the
biosynthetic origin of the second most abundant UV filter compound,
4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid O-β-d-glucoside.
methods. Human lenses were analyzed by high-performance liquid chromatography
(HPLC) after separate incubation with 3H-tryptophan
(3H-Trp), β-benzoylacrylic acid, d,l-α-amino-β-benzoylpropionic acid, or d,l-3-hydroxykynurenine O-β-d-glucoside. The effect of pH on the
model compound d,l-α-amino-β-benzoylpropionic acid and d,l-3-hydroxykynurenine O-β-d-glucoside was also investigated.
results. UV filters were not detected in fetal lenses, despite a 5-month
postnatal lens displaying measurable levels of UV filters. In adults no
radiolabel was incorporated into
4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid O-β-d-glucoside after 3H-Trp
incubations. β-Benzoylacrylic acid was readily reduced in lenses. d,l-α-Amino-β-benzoylpropionic acid and d,l-3-hydroxykynurenine O-β-d-glucoside slowly deaminated at
physiological pH and were converted to β-benzoylpropionic acid and
4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid O-β-d-glucoside, respectively, after lens
conclusions. UV filter biosynthesis appears to be activated at or near birth.
Compounds containing the kynurenine side chain slowly deaminate, and in
the lens, the newly formed double bond is rapidly reduced. These
findings suggest that 4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid O-β-d-glucoside is derived from l-3-hydroxykynurenine O-β-d-glucoside through this
deamination-reduction process. The slowness of the deamination
presumably accounts for the absence of incorporation of radiolabel from 3H-Trp into 4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid O-β-d-glucoside.
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