Control of the Hyaluronidase Activity Towards Hyaluronan by Formation of Electrostatic Complexes: Fundamental and Application Relevance - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 130

HA concentration, the initial hydrolysis rate increased when the ionic strength was
increased. In fact, Bollet et al. (1963) already reported such a low hydrolysis rate at
high HA concentration with rat kidney HAase in 0.10 mol l -1 acetate buffer at pH 3.8.
Similarly, Aronson and Davidson (1967) mentioned that rat liver HAase in 0.10 mol
l -1 acetate buffer at pH 3.9 exhibited inhibition at high HA concentration and that this
inhibition was prevented by 0.15 mol l -1 sodium chloride. Nevertheless, these authors
did not provide any explanation for their results.
Figure 4. Substrate-dependence of the HA hydrolysis catalyzed by BT-HAase at pH 4 and at 37°C, for
different sodium chloride concentrations ranging from 0 to 0.3 mol l -1 . The BT-HAase concentration
was 0.2 g l -1 . The number average molar mass of HA was 0.97 × 10 6 g mol -1 . (unpublished personal
data).
In order to explain the atypical behavior of the HA/BT-HAase system, we inves-
tigated several hypotheses including a classical inhibition by an excess of substrate,
a steric exclusion effect so that the enzyme would not be able to get close enough to
any cleavable bonds of the HA molecule and a viscosity effect which would reduce
the HAase diffusion rate. However, none of these hypotheses could explain all the
experimental results and so, they could not be responsible by themselves for the atypi-
cal behavior of the HA/BT-HAase system (Asteriou et al., 2006). In fact, the only
one receivable explanation for the atypical behavior was based on the idea according