Catalyzes the phosphorylation of hexose (six-carbon sugars) to hexose 6-phosphate (PubMed:8549830, PubMed:9790975). Phosphorylates D-fructose, D-mannose and, to a lower extent, D-glucose (PubMed:8549830, PubMed:9790975). Compared to hxk2, has low affinity for D-glucose (PubMed:8549830, PubMed:9790975). ATP + D-hexose = ADP + D-hexose 6-phosphate + H(+) ATP + D-mannose = ADP + D-mannose 6-phosphate + H(+) ATP + D-fructose = ADP + D-fructose 6-phosphate + H(+) ATP + D-glucose = ADP + D-glucose 6-phosphate + H(+) Carbohydrate metabolism; hexose metabolism. Carbohydrate degradation; glycolysis; D-glyceraldehyde 3-phosphate and glycerone phosphate from D-glucose: step 1/4. Monomer. Belongs to the hexokinase family.