Biomolecular Interaction of Matrix Metalloproteinases and Their Inhibitors TlMPs
291
related to the serralysins (bacterial proteases from Serratia, Pseudomonas and
Erwinia), the adamalysins (also called reprolysins or ADAMs) and the astacins
(meprins, tolloids, "hatching enzymes") (Bode et al. 1993).
Because of their individual domain structure matrix metalloproteinases can be
divided into matrilysin, MMPs with a hemopexin like domain, MMPs with a
transmembrane domain and MMPs with a fibronectin like domain.
The hydrophobic signal peptide mediates intracellular sorting and is removed
during secretion of the proenzyme. Its latency is maintained by the propeptide
with the highly conserved sequence PRCGVPD that complexes the active site zinc
ion with the thiol group of the cysteine residue and is removed in a stepwise process upon activation (Knauper et al. 1990, Tschesche et al. 1992, Nagase et al.
1990) including the disruption of the thiol-zinc interaction, the so-called
"cysteine-switch" (Springman et al. 1990). For example, in vitro activation of the
neutrophil pro collagenase (MMP-8) initiated by proteinases, mercurials or oxidants leads to active species having either Phe79, Met80 or Leu81 as the Nterminal residue and differing significantly in activity (Blaser et al. 1991, Grant et
al. 1987, Knauper et al. 1990, Knauper et al. 1993, Mallya et al. 1990, Suzuki et al.
1990). The species upon stromelysin-1 activation is the Phe79 form and because
it is approximately 3.5-fold more active than the two other species, this phenomenon has been called "superactivation" (Knauper et al. 1993, Reinemer et al. 1994).
Likewise fibroblast collagenase (MMP-l) can be "superactivated" by stromelysin1 with an increase of proteolytic activity up to 12-fold (He et al. 1989, Murphy et
al. 1987, Suzuki et al. 1990). Both the catalytic domain of MMP-8 with the
N-terminal Phe79 and the N-terminal Met80 have been expressed in E. coli
(Reinemer et al. 1994, Schnierer et al. 1993) and crystallized (Bode et al. 1994,
Reinemer et al. 1994).
Determination of their X-ray structures has revealed that the N-terminal
Phe79 ammonium group makes a salt link with the side chain carboxylate group
of Asp232. Therefore, the N-terminal peptide is tightly packed against a hydrophobic surface groove made by a C-terminal helix and a descending segment
centering around the third His ligand of the catalytic zinc ion. The attachment of
this N -terminal heptameric segment probably results in stabilization of the catalytic site via strong hydrogen bonds mediated by the adjacent Asp233 with the
"Met-turn", that forms the base of the active site residues (Reinemer et al. 1994).
Correspondingly, the N-terminal peptide of the Met80 variant is too short to
form a salt bridge with Asp 232, so that the N-terminal segment is less ordered
and not localized in the X-ray structure analysis (Fig. 21.2, arrow). The lack of
active site stabilization or interference of this segment with substrate binding
might be an explanation for the lower enzymatic activity.
In vivo the activation of matrix metalloproteinases is a relatively complex process, because several soluble and membrane-bound proteases, receptors and
inhibitors can be involved in the processing of the propeptide. Activation cascades by cathepsins and serine proteases, (pro )plasminogen activator and receptor, plasminogen and plasminogen receptor and finally active plasminogen have
been described as well as induction of the "cysteine switch" by bacterial proteases
and activated MMPs (for a review see Nagase 1997). Moreover furin seems to
activate prostromelysin-3 (MMP-ll) already intracellulady, so that it is secreted
291
related to the serralysins (bacterial proteases from Serratia, Pseudomonas and
Erwinia), the adamalysins (also called reprolysins or ADAMs) and the astacins
(meprins, tolloids, "hatching enzymes") (Bode et al. 1993).
Because of their individual domain structure matrix metalloproteinases can be
divided into matrilysin, MMPs with a hemopexin like domain, MMPs with a
transmembrane domain and MMPs with a fibronectin like domain.
The hydrophobic signal peptide mediates intracellular sorting and is removed
during secretion of the proenzyme. Its latency is maintained by the propeptide
with the highly conserved sequence PRCGVPD that complexes the active site zinc
ion with the thiol group of the cysteine residue and is removed in a stepwise process upon activation (Knauper et al. 1990, Tschesche et al. 1992, Nagase et al.
1990) including the disruption of the thiol-zinc interaction, the so-called
"cysteine-switch" (Springman et al. 1990). For example, in vitro activation of the
neutrophil pro collagenase (MMP-8) initiated by proteinases, mercurials or oxidants leads to active species having either Phe79, Met80 or Leu81 as the Nterminal residue and differing significantly in activity (Blaser et al. 1991, Grant et
al. 1987, Knauper et al. 1990, Knauper et al. 1993, Mallya et al. 1990, Suzuki et al.
1990). The species upon stromelysin-1 activation is the Phe79 form and because
it is approximately 3.5-fold more active than the two other species, this phenomenon has been called "superactivation" (Knauper et al. 1993, Reinemer et al. 1994).
Likewise fibroblast collagenase (MMP-l) can be "superactivated" by stromelysin1 with an increase of proteolytic activity up to 12-fold (He et al. 1989, Murphy et
al. 1987, Suzuki et al. 1990). Both the catalytic domain of MMP-8 with the
N-terminal Phe79 and the N-terminal Met80 have been expressed in E. coli
(Reinemer et al. 1994, Schnierer et al. 1993) and crystallized (Bode et al. 1994,
Reinemer et al. 1994).
Determination of their X-ray structures has revealed that the N-terminal
Phe79 ammonium group makes a salt link with the side chain carboxylate group
of Asp232. Therefore, the N-terminal peptide is tightly packed against a hydrophobic surface groove made by a C-terminal helix and a descending segment
centering around the third His ligand of the catalytic zinc ion. The attachment of
this N -terminal heptameric segment probably results in stabilization of the catalytic site via strong hydrogen bonds mediated by the adjacent Asp233 with the
"Met-turn", that forms the base of the active site residues (Reinemer et al. 1994).
Correspondingly, the N-terminal peptide of the Met80 variant is too short to
form a salt bridge with Asp 232, so that the N-terminal segment is less ordered
and not localized in the X-ray structure analysis (Fig. 21.2, arrow). The lack of
active site stabilization or interference of this segment with substrate binding
might be an explanation for the lower enzymatic activity.
In vivo the activation of matrix metalloproteinases is a relatively complex process, because several soluble and membrane-bound proteases, receptors and
inhibitors can be involved in the processing of the propeptide. Activation cascades by cathepsins and serine proteases, (pro )plasminogen activator and receptor, plasminogen and plasminogen receptor and finally active plasminogen have
been described as well as induction of the "cysteine switch" by bacterial proteases
and activated MMPs (for a review see Nagase 1997). Moreover furin seems to
activate prostromelysin-3 (MMP-ll) already intracellulady, so that it is secreted