Involved in the synthesis of the GDP-mannose and dolichol-phosphate-mannose required for a number of critical mannosyl transfer reactions. alpha-D-mannose 1-phosphate = D-mannose 6-phosphate Nucleotide-sugar biosynthesis; GDP-alpha-D-mannose biosynthesis; alpha-D-mannose 1-phosphate from D-fructose 6-phosphate: step 2/2. Homodimer. Belongs to the eukaryotic PMM family.