The first endogenous matrix-metalloproteinase NtMMP1 from tobacco BY-2 cells was characterized in detail. Transgenic BY-2 cell lines expressing antisense-RNA against different endogenous proteases (aspartic, cysteine, matrix-metallo and serine) separately (single-antisense) or simultaneously (multi-antisense) was generated. The inhibition of endogenous protease(s) in those lines was verified and the stability of recombinant protein(s) was tested.
