An artificial bifunctional enzyme, gamma-glutamyl kinase/gamma-glutamyl phosphate reductase, was obtained by fusing the Escherichia coil genes proA and proB. The proB gene was fused to the 5’-end of the proA gene with a linker encoding five amino acids. When expressed in E. coil enhanced intracellular concentrations of proline were observed. At 0.6 M NaCl the growth rates for the strain carrying the fusion enzyme and a control harbouring a plasmid encoding the wild-type enzymes were 320 and 530 min, respectively.