Using the structural gene of a homo dimeric enzyme, the water-soluble pyrroloquinoline quinone glucose dehydrogenase (PQQGDH-B), a gene consisting of two identical subunits linked together by a DNA segment coding linker peptide region was constructed. Using the constructed gene, a linked-dimeric PQQGDH-B was produced in Escherichia coli as the active soluble enzyme. Linked-dimeric PQQGDH-B showed a larger increase in thermal stability than the native dimeric enzyme. During incubation over 45 degrees C, the residual activity of linked-dimeric PQQGDH-B was more than twice that of the native dimeric enzyme. The potential application of linked-dimeric PQQGDH-B for glucose enzyme sensor is also discussed.