Involved in the catabolism of D-glucosaminate. Catalyzes the conversion of keto-3-deoxygluconate 6-phosphate (KDGP) to yield pyruvate and glyceraldehyde-3-phosphate. 2-dehydro-3-deoxy-6-phospho-D-gluconate = D-glyceraldehyde 3-phosphate + pyruvate By D-glucosaminate and DgaR. Cells lacking this gene are able to grow with D-glucosaminate as the sole carbon source, although the growth rate is significantly lower. Belongs to the DagF family.