The present invention relates to a process for producing recombinant desulphatohirudin by means of culturing microorganisms. Concerning the codon usage of microorganisms the synthesized nucleotide sequences were joined downstream of and in reading frame with isolated promoters and signal sequences, subsequently the expression/secretion cassettes comprising the foregoing elements were inserted into plasmid DNAs allowing the cultivation of cells under selective culture conditions. E. coli, Saccharomyces and Streptomyces species were transformed with the said recombinant plasmids to biosynthesize the thrombin inhibitor desulphatohirudin HV-1 which was then isolated and identified. The thus-produced desulphatohirudin can be used to inhibit blood coagulation.