Biomedical Engineering Reference
In-Depth Information
All these results clearly indicate that the BT-HAase activity towards HA can be
either enhance or suppress by formation of electrostatic complexes. The BT-HAase
activity can be enhance by polycations, which
in vivo
are mainly proteins, to the con-
dition that (i) they are able, by forming electrostatic complexes with HA, to avoid, or
at least to limit, the formation of electrostatic complexes between HA and BT-HAase
and, (ii) the ratio of the polycation over HA quantities in the HA-polycation complexes
allows enough HA b(1,4) bonds to remain accessible to BT-HAase. Suppression of
the BT-HAase activity may result from the formation of two types of electrostatic
complexes: (i) HA-polycation complexes in which the accessibility of BT-HAase to
the HA b(1,4) bonds is hindered because of a too high value of the ratio of the polyca-
tion over HA quantities in the complexes and, (ii) polyanion-BT-HAase complexes in
which BT-HAase is catalytically inactive. In our study, the only one polyanion was
HA and we showed that it is able to form electrostatic complexes with BT-HAase
in which BT-HAase is catalytically inactive. Nevertheless, many polyanions, includ-
ing GAG other than HA (heparin, heparan sulfate, dermatan sulfate), HA derivatives
(O-sulfonated HA) and synthetic polyanions (poly(styrene-4-sulfonate)) are known to
inhibit HAase (Aronson and Davidson, 1967; Girish and Kemparaju, 2005; Isoyama
et al., 2006; Mathews and Dorfman, 1955; Toida et al., 1999). In the case of heparin,
Maksimenko et al. (2001) demonstrated that the inhibition results from the formation
of electrostatic heparin-HAase complexes.
releVaNCe oF the ProCess oF eNhaNCemeNt/suPPressioN oF the
haase aCtiVity By FormatioN oF eleCtrostatiC ComPleXes
The results of our studies of the BT-HAase activity towards HA clearly show that the
enzymatic activity of BT-HAase can be strongly modulated by formation of electro-
static complexes involving either HA or BT-HAase or both. The question then is what
could be the role of the process of enhancement/suppression of the HAase activity by
formation of electrostatic complexes under
in vitro
and
in vivo
conditions? Concerning
in
vitro
conditions, we show below that it could play an important role in the detection,
quantification, characterization and use of HAase. In the case of
in vivo
conditions,
even though it is much more difficult to unambiguously demonstrate the role of the
process of enhancement/suppression of the HAase activity by formation of electro-
static complexes, this question is discussed below on the basis of experimental data
related to the involvement of HA and HAase in cancer.
Detection, Quantification, Characterization and use of HAase
The ability of HA and HAase to form electrostatic complexes either with each other
or with other polyelectrolytes very probably accounts for some of the difficulties en-
countered in attempts to detect, to quantify and to characterize HAase activity. Indeed,
in addition to being present at exceedingly low concentration (Stern, 2005), it was
observed by some authors that for highly purified HAase preparations no enzymatic
activity was detectable in the absence of added proteins (Maingonnat et al., 1999;
Mathews and Dorfman, 1955). According to our results, we may suggest that when
these purified HAase preparations were mixed with HA, HAase underwent electro-
static complex formation with HA and was thus unable to catalyze HA hydrolysis. We
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