| Transaldolase (TAL) is an essential enzyme of the non-oxidative part of the pentose phosphate pathway(ppp) with produces reductive potential in the form of NADPH as well as ribose 5-phosphate for incorporation into nucleotides . NAPDH is not only a reductor to keep glutathione reducted , but also a H~+ supplier for many metabolic pathways. Recent studies have shown that Transaldolase plays an important role in the development of Multiple Sclerosis, malignant tumor, Liver Cirrhosis organ development and embryogenesis, and also functions in some factors induced apoptosis. The expression and activation of Tranaldolase have tissue-specificity, correlating with the different develop phase and the difference between physiological and pathological condition.Previous study of Peter's lab had demonstrated that In the liver tumors, transaldolase activity was increased 1.5- to 3.4-fold over the activities observed in normal control rat liver,while it showed no change in the regenerating liver.Meanwhile, study of Banki group showed that Transaldolase functions was related to the malignant tumor development.Due to the high conservation of Transaldolase gene and the homology of Transaldolase protein structure in defferent creature. We are trying to study the potential role of Transaldolase on human hepatocarcinogenesisThe study was divided into two parts: the first part was to study the activity of Transaldolase in the hepatocellular carcinoma tissues and the expression level of Transaldolase in hepatocellular carcinoma tissue and normal tissue at mRNA and protein level. The second part was to probe whether Transaldolase has any isoforms.and research on the relationship between Transaldolase activity and post-translational modification. We set out to indicate the function of Transaldolase in the molecular mechanism of tumor development.1 The high activity of Transaldolase in the human hepatocellular carcinomaWe measured the activity of Transaldolase in normol liver , pericancerous land hepatocellular carcinoma tissues by the method described by Lachaise, and using PT-PCR and SDS-PAGE, Western blotting Transaldolase expression in mRNA level and protein level were determined. Our results showed that the activity of Transaldolase was much higher in the carcinoma tissue than it in the normal tissue or tissue around the tumor, but the expression levels of both messenger and protein are no significant difference. The change of activity may be associated with post-translational modification. This is a discovery which not reported in human carcinoma.Previous studies had demonstrated that nucleotide composition is well related to ribose 5-phosphate, thus Transaldolase may be a vital rolein the occurrence of hepacellular carcinoma by regulating the quantity of ribose 5-phosphate in the ppp. It would be a new path on study in hepacarcitogenesis. It is likely to inhibit the growth of cacinoma by controlling the activity of Transaldolase . 2 The expression of Transaldolase in the hepacellular carcinomaWe did 2-Dimentional electriphoresis Western blotting to check the protein level of Transaldolase in the hepatocellular carcinoma tissue. We separated more than 10 isoforms of Transaldolase. The a7 spot was hardly expressed in normol liver , while in hepacellular carcinoma it was highly expressed. The rapid growth of hepacellular carcinoma accompanies high frequency of cell metabolism, which may cause the over expression of Transaldolase gene. The a7 spot was highly expressed in hepacellular carcinoma, so it may be related to hepacarcitogenesis . The a2 spot was markly decreased in hepatoma, which indicated the change of activity may be associated with post-translational modification.These results show that Transaldolase is a key enzyme which maintain the well-balanced cellular function. In addition, Transaldolase may play a crucial role in pathological changes and may be a marker. It is a question for discussion to research for other function of the well-informed enzyme in carbohydrate metabolism.
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