Self-similarity of Mn(II)-induced trypsin activity oscillations. Experimental evidence

Aperiodic self-similar oscillations of trypsin activity were shown by experiments conducted in the presence of Mn2+ ion at pH 8.2 and -10 degrees C in frozen (cryo-oscillations) and at 0 degrees and 25 degrees C under unstirred conditions, respectively. The solution of trypsin obtained by trypsinogen activation and of 0.1 M MnCl2 was distributed into samples or kept in batches at the experimental temperature and sampled. At given time intervals the samples were tested for tryptic activity. In experiments at -10 degrees C the samples were frozen at the initiating of the series. The irregular shapes of activity curves as well as the trajectory of a next-amplitude plot is discussed as a result of a sensitive coupling between the chemical/conformational and diffusional controls of the enzyme activity in the far-from-equilibrium heterogeneous system. These indicate that the self-similar character of the trypsin activity oscillations can be considered on a phenomenological level.