Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency plays an important biochemical role in the metabolism of the lens. Controversies exist in the literature on the possible association between G-6-PD deficiency and the development of cataracts. The authors present ten patients, aged between infancy and 40 years of age, who were admitted for bilateral congenital or presenile cataracts. These patients had no ocular or systemic disease which might have caused their cataract. The only systemic finding they had was G-6-PD deficiency. Two other patients among the families described suffered from bilateral congenital or presenile cataracts with no G-6-PD deficiency. This deficiency state does not appear to play a role in the production of their cataracts.
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PMID:Cataracts in glucose-6-phosphate dehydrogenase deficiency. 823 57

Glucose-6-phosphate dehydrogenase (G6PDH) is an important lens enzyme diverting about 14% of the tissue glucose to the hexose monophosphate shunt pathway. The main function of such a pronounced activity of the enzyme is to support reductive biosyntheses, as well as to maintain a reducing environment in the tissue so as to prevent oxy-radical induced damage and consequent cataract formation. Sugars are one of the well-known cataractogenic agents. Several reports suggest that the cataractogenic effect of the sugars in diabetes as well as in normal aging is initiated by the glycation of the proteins including the enzymes and subsequent formation of more complex and biologically inactive or harmful structures. In a diabetic lens the concentration of fructose exceeds significantly the concentration of glucose, suggesting that the contribution of fructosylation may be greater than that of glucosylation. These studies were undertaken to examine further the possibility that in addition to glycation, generation of oxygen free radicals by fructose and consequent oxidative modifications in certain enzymes may be an important participant in the cataractogenic process. This hypothesis was tested by using G6PDH. The enzyme was incubated with various levels of fructose (0-20mM) and its activity determined as a function of time. This led to a significant loss of its activity, which was prevented by superoxide dismutase, catalase, mannitol and myoinositol. Most interestingly, pyruvate at levels between 0.2 and 1.0 mM also offered substantial protection. Hence, the results, while elucidating further the mechanism of enzyme deactivation by sugars such as fructose, also demonstrate the possibility of therapeutic prevention of cataracts by pyruvate and other such keto acids, in diabetes and other disabilities involving oxygen free radicals in the pathogenetic process.
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PMID:Fructose induced deactivation of glucose-6-phosphate dehydrogenase activity and its prevention by pyruvate: implications in cataract prevention. 986 46