STABILITY AND STABILIZATION OF ENZYMES FROM MESOPHILIC AND THERMOPHILIC ORGANISMS IN RESPECT TO THEIR USE IN FIA-SYSTEMS FOR THE DETERMINATION OF L-LACTATE AND ACETATE

The stabilization effect of 'bilayer encagement' on enzymes from mesop hilic organisms and their 'thermophilic' counterparts was compared. La ctate dehydrogenases from pig heart and from a thermophilic bacterium (Clostridium thermohydrosulfuricum), respectively, showed stabilizatio n factors of 4.5 (at 47 degrees C) and 12.8 (at 70 degrees C), respect ively. For 'thermophilic' acetate kinase no stabilization effect of en cagement was observed. Lactate dehydrogenase and acetate kinase from C lostridium thermohydrosulfuricum were immobilized to controlled porous glass and tested for their long-term stability. The 'thermophilic' en zymes showed by far a longer half-life as compared with the correspond ing enzymes from pig heart and Escherichia coli, respectively, the hal f-life time of the flow injection system response with thermophilic la ctate dehydrogenase at 35 degrees C attaining 250 h (mesophilic enzyme 89 h), and with thermophilic acetate kinase 79 h (mesophilic enzyme 2 4 h).