beta-D-fructose 6-phosphate + GDP-alpha-D-mannose = beta-D-fructofuranosyl alpha-D-mannopyranoside 6(F)-phosphate + GDP + H(+) Optimum pH is 8.0. Carbohydrate metabolism; mannosylfructose biosynthesis; beta-D-fructofuranosyl alpha-D-mannopyranoside from D-fructose 6-phosphate and GDP-alpha-D-mannose: step 1/2. By salt. Belongs to the glycosyltransferase 1 family. Truncated N-terminus.