Nucleic acid construct for expressing active substances which can be activated by proteases, and preparation and use

A polypeptide encoded by a nucleic acid construct comprising the following nucleic acid sequences in the following order:

• a) at least one promoter element comprising the promoter sequence of the cdc25C gene, the sequence GCCACC, and the cDNA for an immunoglobulin signal peptide operably linked to;
• b) at least one nucleic acid sequence which encodes human factor X, in which amino acid 194 has been mutated from Arg to Tyr (mutated FX), operably linked to;
• c) at least one nucleic acid sequence which encodes an amino acid sequence cleavable specifically by a protease which is released at or from a mammalian target cell, operably linked to;
• d) at least one DNA sequence which encodes a polypeptide which is bound to said mutated FX by said cleavable amino acid sequence and inhibits the activity of said
• compound while bound thereto by said cleavable amino acid sequence, wherein said polypeptide comprises the mutated FX of b), the cleavable sequence or sequences of c), and the inhibitor or inhibitors of d), and wherein said nucleic acid component c) does not naturally occur as operably linking said nucleic acid sequence b) to said nucleic acid d) and wherein the nucleic acid sequence b)c)d) encodes an inactive precursor of the mutated FX, compound b).