A method for producing 2-keto-3-deoxygluconate (KDG) from 2-(acetylamino)-2-deoxy-D-gluconic acid (GlcNAc1A) by two enzymes; GlcNAc1A is converted to KDG by incubating GlcNAc1A with a deacetylase OngB at 25° C. for 4-12 h and then with a deaminase OngC at 25° C. for another 10-15 h; it constructs two engineered E. coli/pET22b-ongB (carrying the ongB gene) and E. coli/pET22b-ongC (carrying the ongC gene) strains to prepare recombinant proteins OngB and OngC, respectively; at the action of these two enzymes, OngB and OngC, GlcNAc1A is converted to KDG, which solves the bottleneck of GlcNAc1A utilization during the bioconversion of chitin; the KDG is an important metabolic intermediate to synthesize furan derivatives, herbicides, food additives and other industrially important chemical compounds, having wide industrial applications.