Domain specific characteristics of the bifunctional key enzyme of sialic acid biosynthesis, UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase

Item Type:	Article
Title:	Domain specific characteristics of the bifunctional key enzyme of sialic acid biosynthesis, UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase
Creators Name:	Blume, A. and Weidemann, W. and Stelzl, U. and Wanker, E.E. and Lucka, L. and Donner, P. and Reutter, W. and Horstkorte, R. and Hinderlich, S.
Abstract:	UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase is a bifunctional enzyme, which initiates and regulates sialic acid biosynthesis. Sialic acids are important compounds of mammalian glycoconjugates, mediating several biological processes, such as cell-cell or cell-matrix interactions. In order to characterize the function of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase, a number of deletion mutants were generated, lacking either parts of the N-terminal epimerase or the C-terminal kinase domain. N-terminal deletion of only 39 amino acids results in a complete loss of epimerase activity. Deletions in the C-terminal part result in a reduction or complete loss of kinase activity, depending on the size of the deletion. Deletions at either the N- or the C-terminus also result in a reduction of the other enzyme activity. These results indicate that a separate expression of both domains is possible, but that a strong intramolecular dependency of the two domains has arisen during evolution of the enzyme. N-terminal, as well as C-terminal, mutants tend to form trimers, in addition to the hexameric structure of the native enzyme. These results and yeast two-hybrid experiments show that structures required for dimerization are localized within the kinase domain, and a potential trimerization site is possibly located in a region between the two domains. In conclusion, our results reveal that the activities, as well as the oligomeric structure, of this bifunctional enzyme seem to be organized and regulated in a complex manner.
Keywords:	Deletion Mutant, Domain, Sialic Acid, UDP-N-Acetylglucosamine 2-Epimerase, Yeast Two-Hybrid Assay, Animals, Rats
Source:	Biochemical Journal
ISSN:	0264-6021
Publisher:	Portland Press
Volume:	384
Number:	3
Page Range:	599-607
Date:	26 August 2004
Official Publication:	https://doi.org/10.1042/BJ20040917
PubMed:	View item in PubMed

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