TAILIEUCHUNG - Báo cáo khóa học: UDPgalactose 4-epimerase from Saccharomyces cerevisiae A bifunctional enzyme with aldose 1-epimerase activity

UDPgalactose 4-epimerase (epimerase) catalyzes the reversible conversion between UDPgalactose and UDPglu-cose and is an important enzyme ofthe galactose metabolic pathway. TheSaccharomyces cerevisiaeepimerase encoded by theGAL10gene is about twice the size ofeither the bacterial or human protein. Sequence analysis indicates that the yeast epimerase has an N-terminal domain (residues 1–377) that shows significant similaritywithEscherichia coli and human UDPgalactose 4-epimerase, and a C-terminal domain (residues 378–699), which shows extensive identity to either the bacterial or human aldose 1-epimerase (muta-rotase) | Eur. J. Biochem. 271 753-759 2004 FEBS 2004 doi UDPgalactose 4-epimerase from Saccharomyces cerevisiae A bifunctional enzyme with aldose 1-epimerase activity Siddhartha Majumdar1 Jhuma Ghatak2 Sucheta Mukherji2 Hiranmoy Bhattacharjee3 and Amar Bhaduri 1 Division of Drug Design Development and Molecular Modeling and 2Division of Cellular Physiology Indian Institute of Chemical Biology Kolkata India 3Department of Biochemistry and Molecular Biology Wayne State University School of Medicine Detroit MI USA UDPgalactose 4-epimerase epimerase catalyzes the reversible conversion between UDPgalactose and UDPglu-cose and is an important enzyme of the galactose metahoiic pathway. The Saccharomyces cerevisiae epimerase encoded by the GAL10 gene is about twice the size of ei thrr the bacterial or human protein. Sequence analysis indicates that the yeast epimerase has an N-terminal domain residues 1-377 that shows significant similarity with Escherichia coli and human UDPgalactose 4-epimerase and a C-terminal domain residues 378-699 which shows extensive identity to either the bacterial or human aldose 1-epimerase muta-rotase . The S. cerevisiae epimerase was purified to 95 homogeneity by sequential chromatography on DEAE-Sephacel and Resource-Q columns. Purified epimerase preparations showed mutarotase activity and could convert either a-D-glucose or a-D-galactose to their b-anomers. Induction of cells with gNac-tose tai to simuttonsuus enhancement ofboth epimerase and mutarotase activities. Size exclusion chromatography experiments confirmed that the mutarotase activity is an intrinsic property ofthe yeast epimerase and not due to a copurifying endogenous muta-rotase. When the purified protein was treated with 5 -UMP and L-arabinose epimerase activity was completely lost but the mutarotase activity remained unaffected. These results demonstrate that the S. cerevisiae UDPgalactose 4-epi-merase is a bifunctional enzyme with aldose 1-epimerase .

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