Pernisine, extracellular protease from hyper thermophilic archaea Aeropyrum pernix, is active in wide temperature and pH range. Secreted (extracellular) enzymes can be attached to the membrane or they can be free. The goal of this thesis was to determine whether pernisine is attached or free enzyme. Recombinant pernisine was produced in Escherichia coli, and liposomes, simplified models of cell membranes were prepared from archaeal lipids. With sedimentation test and azocasein test we showed that pernisine does not bind to the liposomes from archaeal lipids (archeosomes). Using several methods (fluorescence emission spectroscopy, circular dichroism, measurements of fluorescence polarization with membrane probe diphenylhexatriene) we showed that the secondary structure of pernisine in presence of liposomes is not changed significantly, which confirms the absence of hydrophobic interactions between pernisine and archeosomes. Using methods described above we concluded that pernisine is a free enzyme. Free enzymes are significant for biofilms, so we assumed that A. pernix is also forming biofilms. In flasks where archaea were cultivated, we observed a thin film. With zymogram we detected proteolytical activity in this film, which confirms our hypothesis that A. pernix is forming biofilms that consist of pernisine.