1did
From Proteopedia
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OBSERVATIONS OF REACTION INTERMEDIATES AND THE MECHANISM OF ALDOSE-KETOSE INTERCONVERSION BY D-XYLOSE ISOMERASE
Overview
Crystallographic studies of D-xylose isomerase (D-xylose ketol-isomerase, EC 5.3.1.5) incubated to equilibrium with substrate/product mixtures of, xylose and xylulose show electron density for a bound intermediate. The, accumulation of this bound intermediate shows that the mechanism is a, non-Michaelis type. Carrell et al. [Carrell, H. L., Glusker, J. P., Burger, V., Manfre, F., Tritsch, D. & Biellmann, J.-F. (1989) Proc. Natl., Acad. Sci. USA 86, 4440-4444] and the present authors studied crystals of, the enzyme-substrate complex under different conditions and made different, interpretations of the substrate density, leading to different conclusions, about the enzyme mechanism. All authors agree that the bound intermediate, of the sugar is in an open-chain form. It is suggested that the, higher-temperature study of Carrell et al. may have produced an, equilibrium of multiple states, whose density fits poorly to the, open-chain substrate, and led to incorrect interpretation. The two groups, also bound different closed-ring sugar analogues to the enzyme, but these, analogues bind differently. A possible explanation consistent with all the, data is that the enzyme operates by a hydride shift mechanism.
About this Structure
1DID is a Single protein structure of sequence from Arthrobacter sp. with DIG and MN as ligands. Active as Xylose isomerase, with EC number 5.3.1.5 Full crystallographic information is available from OCA.
Reference
Observations of reaction intermediates and the mechanism of aldose-ketose interconversion by D-xylose isomerase., Collyer CA, Blow DM, Proc Natl Acad Sci U S A. 1990 Feb;87(4):1362-6. PMID:2304904
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