Mechanism Sucrose-phosphate synthase

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reaction scheme showing hexosyl group transfer udp-glucose fructose 6-phosphate.


in open conformation of h. orenii sps, fructose 6-phosphate forms hydrogen bonds gly-33 , gln-35 residues in domain while udp-glucose interacts b-domain. crystal structures studies reveal after binding, 2 domains twist narrow entrance of substrate binding cleft 20 Å 6 Å. in closed conformation, gly-34 residue of domain interacts udp-glucose , forces substrate adapt folded structure, facilitating donation of hexosyl group. after binding, fructose 6-phosphate interact udp via hydrogen bond, lowers activation energy of reaction , stabilizes transition state. finally, c1 atom of udp-glucose undergoes nucleophilic attack oxygen atom in fructose 6-phosphate, resulting in glucosyl group transfer fructose 6-phosphate. whether or not mechanism requires divalent ion unclear, failed attempts trap , detect presence of magnesium cation suggest mechanism metal ion independent.








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