Редактирование: TKT

Transketolase (EC 2.2.1.1) (TK)

==Publications==

{{medline-entry
|title=Transketolase gene expression in the cornea is influenced by environmental factors and developmentally controlled events.
|pubmed-url=https://pubmed.ncbi.nlm.nih.gov/11095059
|abstract=Transketolase ([[TKT]]) has been proposed to be a corneal crystallin, and its gene and protein are abundantly expressed in the corneal epithelium of several mammals. A marked up-regulation of [[TKT]] gene expression coincides with the time of eyelid opening in the mouse. Here, we examined whether exposure to incident light contributes to the up-regulation of [[TKT]] gene expression during cornea maturation. Mice were raised in either standard light/dark cycling conditions or total darkness. In some cases, subcutaneous injections of epidermal growth factor ([[EGF]]) were given beginning on the day of birth to induce early eyelid opening. RNA was prepared from the corneas of mothers and pups and subjected to Northern blot analyses. In addition, the relative levels of [[TKT]] mRNA and/or enzyme activity were examined in the corneas of human, bovine, rat, chicken, and zebrafish. [[TKT]] mRNA levels were 2.1-fold higher in the corneas of 25-day-old mouse pups ( 12 days after eyelid opening) that had been born and raised in light/dark conditions compared to pups born and raised in total darkness. By contrast, the level of [[TKT]] mRNA in the mature corneas of adult mice maintained in the dark for 2-8 weeks did not vary greatly from those of mice maintained in light/dark conditions. Interestingly, [[TKT]] mRNA levels in the corneas of dark-raised mice, although reduced, did exhibit the increase characteristically observed before and after eyelid opening. In addition, [[TKT]] mRNA levels were elevated fivefold in the corneas of 28-day-old mice raised in darkness and injected with [[EGF]] compared to uninjected mice also deprived of light. The [[EGF]]-injected mice opened their eyes 3 days early, and their corneal epithelium did not grossly differ from that of control mice. [[TKT]] mRNA and/or enzyme activity was found to be much higher in the corneas than in other tissues of humans, bovines, and rats but was extremely low in the corneas of chicken and zebrafish. Our studies suggest that both exposure to incident light and events surrounding the process of eyelid opening play a role in the up-regulation of [[TKT]] gene expression observed during corneal maturation in mice. Light appears to play a less important role in the mature cornea in maintaining high levels of [[TKT]] gene expression. The low levels of [[TKT]] in the cornea of chicken and zebrafish support the notion that [[TKT]] acts as a taxon-specific enzyme-crystallin in mammals. The involvement of environmental signals for this putative, mammalian cornea crystallin contrasts with the purely developmental signals involved in the up-regulation of the crystallin genes of the lens.
|mesh-terms=* Adult
* Aging
* Animals
* Animals, Newborn
* Blotting, Northern
* Cattle
* Cell Line
* Chickens
* Darkness
* Environmental Exposure
* Epidermal Growth Factor
* Epithelium, Corneal
* Female
* Gene Expression
* Humans
* Light
* Male
* Mice
* Pregnancy
* RNA, Messenger
* Rabbits
* Rats
* Transketolase
* Zebrafish

|full-text-url=https://sci-hub.do/10.1097/00003226-200011000-00014
}}
{{medline-entry
|title=Heterogeneous expression of transketolase in ocular tissues.
|pubmed-url=https://pubmed.ncbi.nlm.nih.gov/9154385
|abstract=Previous studies have shown that transketolase is preferentially expressed in the corneal epithelium and comprises up to 10% of the soluble protein of the mature mouse cornea. The aim of this study is to evaluate the expression and distribution of [[TKT]] in the different ocular tissues. We have used in situ hybridization and immunohistochemistry to localize [[TKT]] mRNA and protein in the developing and adult mouse eye. [[TKT]] were found to be widely distributed throughout the adult mouse eye. Among the ocular tissues examined, the corneal epithelium exhibited the highest levels of [[TKT]] mRNA and protein. Within the epithelial layer, [[TKT]] mRNA and protein were differentially distributed with the highest expression occurring in basal cells and the lowest in apical cells, suggesting that [[TKT]] expression in the corneal epithelium may be differentiation-related. Enriched expression of [[TKT]] was also found in the cornea endothelium, lens epithelium, ciliary body, and iris. Low basal levels of expression were observed in the limbus and conjunctiva. In contrast to the adult eye, [[TKT]] expression in the one-day-old mouse eye was homogeneous at low, but detectable levels, suggesting that [[TKT]] expression is developmentally regulated in the cornea as well as in the other ocular tissues. In the healing corneal epithelium, [[TKT]] expression in the single cell layer of the leading edge was completely suppressed until the cells began to stratify, at which point [[TKT]] expression increased markedly. The results presented here suggest that [[TKT]] is differentially expressed and developmentally regulated in the various tissues that comprise the eye.
|mesh-terms=* Aging
* Animals
* Animals, Newborn
* Cornea
* Corneal Injuries
* Eye
* Immunohistochemistry
* In Situ Hybridization
* Mice
* RNA, Messenger
* Tissue Distribution
* Transketolase
* Wound Healing

|full-text-url=https://sci-hub.do/10.1076/ceyr.16.5.467.7042
}}