Mannosylfructose-phosphate synthase (, mannosylfructose-6-phosphate synthase, MFPS) is an enzyme with systematic name GDP-mannose:D-fructose-6-phosphate 2-alpha-D-mannosyltransferase. This enzyme catalyses the following chemical reaction
The enzyme transfers a mannose sugar unit from GDP-mannose to a specific hydroxy group in fructose 6-phosphate (shown in its open-chain form) to give the product disaccharide, with guanosine diphosphate (GDP) as byproduct. It was characterised from the soil proteobacterium and plant pathogen Agrobacterium tumefaciens strain C58, and requires magnesium Mg2+ or manganese Mn2+ ions for activity. The product is hydrolysed by the enzyme mannosylfructose-phosphate phosphatase to give an osmolyte which protects the organism from osmotic shock.
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