The behaviour of enzymes at the air-water interface

Abstract

A study of the behaviour of enzymes at the air-water interface has been conducted in three stages, viz. (i) development of apparatus and technique, (ii) preliminary study of a wide range of enzymes, (iii) detailed study of a limited range of enzymes. The first two stages have been completed, with measurements of pressure-area relationships of enzyme films in the presence and absence of specific substrates, together with associated measurements of viscoelasticity and surface potential. An apparatus is described, which has enabled most of the practical requirements to be satisfied. That useful studies can be made of the effects of specific agents such as substrates, coenzymes and metal ion activators, on the formation and properties of enzyme films has been shown. This exploratory investigation was concerned with the establishment of the principles according to which more precise research on specific characteristics of enzymes might be carried out. The formation and properties of surface films of many enzymes have not been affected by the presence of their substrates. Such enzynes include the proteinases, trypsin, chymo-trypsin and pepsin. In other cases such as aldolase, triosephosphate dehydrogenase, substrates and coenzymes greatly stabilise the tertiary structure of the proteinagainst surface denaturation. When formed these films may show physical evidence of the persistence of complexes in their structure. It is possible from observations of change in spreading rate or visco-elasticity, to estimate values for the dissociation constants of some of these complexes. A fact not previously recorded is that many enzymes, especially those of the extracellular class (e. g. catalase, ribonuclease) show considerable resistance to surface denaturation.