This behaviour could be explained taking into account two effects: (i) the appearance of turbidity in the protein extracts by using enzyme percentages higher than 5% (v/v) and (ii) the so-called competitive inhibition,in which the extracted protein molecules are supposed to act as inhibitors combining with the enzyme to form a complex and thereby preventing its activity, although there is no evidence of this mechanism (Laidler & Bunting, 1973, chap. 3).