Biology Reference
In-Depth Information
RWTNNFREY of MMP-1 is particularly important (Chung et al.
2000
). A single
mutation of Tyr
191
to Thr (the corresponding residue in MMP-3) reduced collage-
nolytic activity to less than 25% and activities against synthetic substrates and
gelatin by more than 90% (Chung et al.
2000
). The peptide bond between Glu
190
and Tyr
191
is in an unusual
cis
configuration (Spurlino et al.
1994
) and Tyr
191
is
conserved in all collagenolytic MMPs except MMP-14 (Woessner and Nagase
2000
). Mutation of the corresponding Tyr
189
of MMP-8 to Phe similarly reduced
collagenolytic activity, but in this case the activity towards a synthetic substrate was
not altered (Pelman et al.
2005
). In addition, Gly
214
located three residues before
the conserved Met in the catalytic domain is important for collagenolysis. Mutation
of this residue to Glu (the corresponding residue in MMP-9) reduces collagenolytic
activity to 0.13% without changing the ability to cleave gelatin (O'Farrell et al.
2006
). It is considered that Gly
214
provides the flexibility necessary to accommo-
date collagen.
5.4 Collagen Type Preference of MMPs
Among six collagenolytic MMPs, MMP-1, -8 and -13 were characterized for their
collagenolytic activities on type I, II and III collagens. MMP-1 cleaves in order of
preference (bovine) type III
type I (guinea pig)
type II (bovine), MMP-8 in
>>
>
order of preference type III
type I
type II andMMP-13 cleaves type II
ΒΌ
type I
>
type III (Tominga, Visse, Nagase, unpublished results). MMP-13 has been consid-
ered to be an important collagenase in cartilage degradation, as the major fibrillar
collagen is type II collagen and Mitchell et al. (
1996
) reported that MMP-13 is a
fivefold better enzyme than MMP-1 in digesting type II collagen. However, the
MMP-1 used in Mitchell's study was activated from the proenzyme by using an
organomercurial compound, 4-aminophenylmercuric acetate, an agent which gen-
erates only 10-20% active MMP-1 (Suzuki et al.
1990
). When fully activated,
MMP-1 has similar collagenolytic activity on type II collagen as MMP-13. None-
theless, MMP-1 cleaves type III and type I collagens much more readily than type II
collagen. Collagen III is therefore much more readily cleaved by MMP-1, but it is a
poor substrate for MMP-13.
Knauper et al. (
1996a
) reported that MMP-13 cleaved type II collagen about five
times faster than type I collagen. We, however, found that MMP-13 cleaves
collagen I (guinea pig) and collagen II (bovine) at a similar rate. This discrepancy
in the two studies may be due to the difference in species of those collagens. Welgus
et al. (
1981a
) found that the
k
cat
/
K
m
value of human MMP-1 against human
collagen I was 66.8
>
>
M
1
h
1
, whereas that against guinea pig collagen I was
m
M
1
h
1
. A more striking difference was observed between human and
guinea pig collagen III with the former being cleaved 16 times more readily than
the latter. Thus, not only collagen types but also species differences for each type of
collagen need to be taken into consideration to study the preferences for the
different types of collagen.
21.7
m
