Exclusive Expression of Transketolase in the Vanadocytes of the Vanadium-Rich Ascidian, Ascidia sydneiensis samea

Biochimica et biophysica acta Volume 1494 Page 83-90 published_at 2000
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Title ( eng )
Exclusive Expression of Transketolase in the Vanadocytes of the Vanadium-Rich Ascidian, Ascidia sydneiensis samea
Creator
Uyama Taro
Kanamori Kan
Michibata Hitoshi
Source Title
Biochimica et biophysica acta
Volume 1494
Start Page 83
End Page 90
Abstract
Ascidians, especially those belonging to the Ascidiidae, are known to accumulate extremely high levels of vanadium in vanadocytes, one type of blood (coelomic) cell. Vanadium, which exists in the +5 oxidation state in seawater, is accumulated in the vanadocytes and reduced to the +3 oxidation state. We have been trying to characterize all of the polypeptides specific to vanadocytes and to specify the proteins that participate in the accumulation and reduction of vanadium. To date, we have localized three enzymes in vanadocytes: 6-phosphogluconate dehydrogenase (6-PGDH: EC 1.1.1.44), glucose-6-phosphate dehydrogenase (G6PDH: EC 1.1.1.49), and glycogen phosphorylase (GP: EC 2.4.1.1), all of which are involved in the pentose phosphate pathway. In the current study, we cloned a cDNA for transketolase, an essential and rate-limiting enzyme in the non-oxidative part of the pentose phosphate pathway, from vanadocytes. The cDNA encoded a protein of 624 amino acids, which showed 61.8 0dentity to the human adult-type transketolase gene product. By immunocytochemistry and immunoblot analyses, the transketolase was revealed to be a protein that was expressed only in vanadocytes and not in any of the more than ten other types of blood cell. This finding, taken together with the localized expression of the other three enzymes, strongly supports the hypothesis that the pentose phosphate pathway functions exclusively in vanadocytes.
Keywords
Chordates
Metal Accumulation
Redox
Gene Expression
NDC
Biology [ 460 ]
Language
eng
Resource Type journal article
Publisher
Elsevier Science B.V.
Date of Issued 2000
Rights
Copyright (c) 2000 Elsevier Science B.V.
Publish Type Author’s Original
Access Rights open access
Source Identifier
[ISSN] 0167-4781
[NCID] AA10506089
[PMID] 11072071
[DOI] 10.1016/S0167-4781(00)00222-0
[DOI] http://dx.doi.org/10.1016/S0167-4781(00)00222-0 isVersionOf