D-mannose 6-phosphate = D-fructose 6-phosphate Binds 1 zinc ion per subunit. Up-regulated by mannose. Is under the control of ManR. Is subject to carbon catabolite repression (CCR) by glucose. Forms part of an operon with manP and yjdF. Cells lacking this gene are unable to grow in minimal medium with mannose as the sole carbon source. They show impaired growth in rich medium, and impairment increases in the presence of greater than 1.4 mM mannose. Belongs to the mannose-6-phosphate isomerase type 1 family.