Document Detail


Molecular cloning and functional analysis of sialyltransferases.
MedLine Citation:
PMID:  8864835     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
To elucidate the regulatory mechanism for carbohydrate expression and to understand the meaning of the carbohydrate-structural diversity, we started to clone sialyltransferase (ST) genes based on two different strategies, i.e. expression and homology cloning. So far, 13 STs have been cloned in our laboratory, 7 of which turned out to be new ones. The primary enzyme structures deduced from all the cloned ST genes suggest a putative domain structure with a type II transmembrane topology. There are no significant amino acid sequence similarities among these cloned STs, except for in two sialyl motifs, L and S, which are proposed to be the CMP-sialic acid recognition and/or catalytic sites. Northern blot analysis revealed the developmental stage-dependent and/or tissue-specific expression of most of the cloned STs. The cloned STs are classified into four families according to the carbohydrate linkages they synthesize, i.e. the ST3Gal-, ST6Gal-, ST6GalNAc-, and ST8Sia-families. Generally, enzymes in these families exhibit strong activity toward certain acceptor groups but show very weak activity toward other acceptor groups, and the substrate specificities of the enzymes overlap one another, as indicated by in vitro experiments. Enzymes in the ST3Gal-family are expressed mainly in a tissue-specific manner. However, those in the ST6GalNAc- and ST8Sia-families are expressed in a tissue-as well as developmental stage-specific manner. In vivo conditions are supposed to be more complex. Therefore, it is quite important to examine their substrate specificities in vivo and the mechanism of their expression to elucidate the physiological role of each enzyme and the meaning of the diversity in carbohydrate structure. Using cloned cDNAs and expressed enzymes, we have been studying how sialylcarbohydrate expression is regulated and what the functions of sialylcarbohydrate chains are. Recently, we found that transfection of the GD3 synthase, an alpha 2,8-ST (ST8Sia I), gene triggers cholinergic neuritogenesis in Neuro2a cells through the de novo expression of GD3, suggesting that the GD3 synthase gene behaves as a neural differentiation inducer.
Authors:
S Tsuji
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review    
Journal Detail:
Title:  Journal of biochemistry     Volume:  120     ISSN:  0021-924X     ISO Abbreviation:  J. Biochem.     Publication Date:  1996 Jul 
Date Detail:
Created Date:  1997-01-14     Completed Date:  1997-01-14     Revised Date:  2007-12-19    
Medline Journal Info:
Nlm Unique ID:  0376600     Medline TA:  J Biochem     Country:  JAPAN    
Other Details:
Languages:  eng     Pagination:  1-13     Citation Subset:  IM    
Affiliation:
Frontier Research Program, Institute of Physical and Chemical Research (RIKEN), Wako, Saitama. setsuji@postman.riken.go.jp
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MeSH Terms
Descriptor/Qualifier:
Amino Acid Sequence
Animals
Carbohydrate Sequence
Cloning, Molecular
Gene Expression Regulation, Enzymologic
Mice
Molecular Sequence Data
Sialyltransferases*
Chemical
Reg. No./Substance:
EC 2.4.99.-/Sialyltransferases

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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