1XEL

UDP-GALACTOSE 4-EPIMERASE FROM ESCHERICHIA COLI

1XEL の概要

• エントリーDOI: 10.2210/pdb1xel/pdb
• 分子名称: UDP-GALACTOSE 4-EPIMERASE, SODIUM ION, NICOTINAMIDE-ADENINE-DINUCLEOTIDE, ... (7 entities in total)
• 機能のキーワード: isomerase
• 由来する生物種: Escherichia coli
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 38737.91

構造登録者

Thoden, J.,Holden, H. (登録日: 1996-01-25, 公開日: 1997-02-12, 最終更新日: 2024-02-14)

主引用文献

Thoden, J.B.,Frey, P.A.,Holden, H.M.
Molecular structure of the NADH/UDP-glucose abortive complex of UDP-galactose 4-epimerase from Escherichia coli: implications for the catalytic mechanism.
Biochemistry, 35:5137-5144, 1996

PubMed Abstract: UDP-galactose 4-epimerase is one of three enzymes in the metabolic pathway that converts galactose into glucose1-phosphate. Specifically this enzyme catalyzes the interconversion of UDP-galactose and UDP-glucose. The molecular structure of the NADH/UDP-glucose abortive complex of the enzyme from Escherichia coli has been determined by X-ray diffraction analysis to a nominal resolution of 1.8 A and refined to an R-factor of 18.2% for all measurement X-ray data. The nicotinamide ring of the dinucleotide adopts the syn conformation in relationship to the ribose. Both the NADH and UDP-glucose are in the proper orientation for a B-side specific transfer from C4 of the sugar to C4 of the dinucleotide. Those residues implicated in glucose binding include Ser 124, tyr 149, Asn 179, Asn199, Arg 231, and Tyr 299. An amino acid sequence alignment of various prokaryotic and eukaryotic epimerases reveals a high degree of conservation with respect to those residues involved in both NADH and substrate binding. The nonstereospecificity displayed by epimerase was originally thought to occur through a simple rotation about the bond between the glycosyl C1 oxygen of the 4-ketose intermediate and the beta-phosphorous of the UDP moiety, thereby allowing the opposite side of the sugar to face the NADH. The present structure reveals that additional rotations about the phosphate backbone of UDP are necessary. Furthermore, the abortive complex model described here suggests that Ser 124 and Tyr 149 are likely to play important roles in the catalytic mechanism of the enzyme.

PubMed: 8611497
DOI: 10.1021/bi9601114

実験手法

X-RAY DIFFRACTION (1.8 Å)