A human prourokinase-like polypeptide having an amino acid sequence represented by the following formula: (Met).Ser¹-X¹⁵⁶.Y¹⁵⁷.Z¹⁵⁸- (wherein Met represents an op­tionally existing methionine, Ser represents serine present at 1-position of the N-terminal, X represents arginine or other amino acid present at 156-position, Y represents proline, glycine, alanine or valine present at 157-position, Z repre­sents lysine or arginine present at 158-position, and the sol­id line represents the same amino acid sequence as that of corresponding part of natural human prourokinase or hu­man urokinase-like polypeptide wherein lysine at 135-posi­tion is replaced by other amino acid than basic amino ac­ids) or having an amino acid sequence substantially the same as this is disclosed. In addition, a DNA segment which codes the above-described polypeptide; a plasmid containing said DNA segment; E. coli transformed by said plasmid; a process for preparing said polypeptide by cultur­ing said E. coli ; a medicine containing said polypeptide; use of said polypeptide for prophylaxis or treatment for forma­tion of thrombus; and use of said polypeptide for preparing the medicine for the above purpose are also disclosed.