PURPOSE: To produce and separate human elastase I, in high efficiency, by carrying out specific transformation and cultivation of a DNA chain having a base sequence coding the polypeptide of amino acid sequences selected from specific three groups.

CONSTITUTION: A DNA chain having a base sequence coding a polypeptide of amino acid sequences selected from specific three groups, is prepared beforehand, and a plasmid containing said DNA chain in a state to enable the exression of the genetic information is prepared. A microbial cell is transformed by the plasmid, and the obtained transformation is cultured to accumulate human elastase I in the culture product. Human elastase I can be produced by the transformed microorganism by this process. Accordingly, the production and separation of human elastase I can be carried out more effectively than the extraction from pancreas.