ABSTRACT
In this chapter we describe recent results on using neutron,
X-ray, and light-scattering methods to analyze structural and
compositional changes due to the action of interfacially active
enzymes on a substrate of low aqueous solubility. The interfacial
mechanism poses challenges in terms of both the structural analysis
of a heterogeneous system and methods to monitor and interpret
the kinetics. Today many of these enzyme systems are used in a
range of applications, including detergency, material science, food
technology, biotechnology, and biofuels. In spite of the growing
industrial relevance, a surprisingly small number of fundamental
studies have been carried out. Here we will address mainly two
classes of important interfacially active enzymes, namely lipolytic
enzymes and cellulases. We will discuss the common features of
the two types of degradation processes, associated with the fact
that these are water-soluble enzymes acting on a substrate surface
that continuously changes due to the enzyme action. One distinctive
difference is the fate of the reaction products, which in the case of
lipolytic enzymes typically remain in the substrate matrix, whereas
the cellulose degradation products are fully soluble. In both cases
the enzymatic process causes changes to the substrate morphology
and structure. Therefore understanding these types of enzymes
requires the use of structural and surface-sensitive techniques that
can determine changes on the nanometer-length scale.