Effects of dimethyl sulfoxide, temperature, and sodium chloride on the activity of human matrix metalloproteinase 7 (matrilysin)

A Method for Screening Enzyme Inhibitors Using Size Exclusion Chromatography and ESI-LC-MS/MS

A pilot study was performed for the development of a method to screen compound libraries using an electrospray mass spectrometer interfaced with liquid chromatography (LC). The mixture of compounds was obtained by combining low-molecular weight inhibitors of carboxypeptidase A (CPA), a representative zinc-containing proteolytic enzyme. After the incubation of the mixture with CPA, the enzyme-bound compounds were separated by size exclusion chromatography (SEC) from unbound compounds. The separation of compounds was affected by LC. Three compounds were identified, which represent the tight binding inhibitors of the library. These compounds were quantitated using an automatic switching valve to avoid the interference of buffer salts with the detection of analytes. The quantitated amounts of the compounds were found to be in good accordance with the Ki values. ( Journal of Biomolecular Screening 2005:30-35)

Effects of salts on the interaction of 8-anilinonaphthalene 1-sulphonate and thermolysin

Neutral salts activate and stabilize thermolysin. In this study, to explore the mechanism, we analyzed the interaction of 8-anilinonaphthalene 1-sulphonate (ANS) and thermolysin by ANS fluorescence. At pH 7.5, the fluorescence of ANS increased and blue-shifted with increasing concentrations (0-2.0 μM) of thermolysin, indicating that the anilinonaphthalene group of ANS binds with thermolysin through hydrophobic interaction. ANS did not alter thermolysin activity. The dissociation constants (Kd) of the complex between ANS and thermolysin was 33 ± 2 μM at 0 M NaCl at pH 7.5, decreased with increasing NaCl concentrations, and reached 9 ± 3 μM at 4 M NaCl. The Kd values were not varied (31-34 μM) in a pH range of 5.5-8.5. This suggests that at high NaCl concentrations, Na(+) and/or Cl(-) ions bind with thermolysin and affect the binding of ANS with thermolysin. Our results also suggest that the activation and stabilization of thermolysin by NaCl are partially brought about by the binding of Na(+) and/or Cl(-) ions with thermolysin.

Effects of heparin and cholesterol sulfate on the activity and stability of human matrix metalloproteinase 7

Sulfated glycosaminoglycans and sulfated lipids are involved in the biological functions of human matrix metalloproteinase 7 (MMP-7). In this study, the effects of heparin and cholesterol sulfate (CS) on the activity and stability of MMP-7 in the hydrolysis of a synthetic substrate, (7-methoxycoumarin-4-yl)acetyl-l-Pro-l-Leu-Gly-l-Leu-[N(3)-(2,4-dinitrophenyl)-l-2,3-diaminopropionyl]-l-Ala-l-Arg-NH2, were examined. Heparin increased activity by decreasing Km, and the Km values for 0 and 50 μM heparin were 57 ± 8 and 19 ± 5 μM, respectively. CS decreased activity in a non-competitive inhibitory manner with a Ki value of 11 ± 3 μM. In thermal incubation at 50-70 °C, heparin increased relative activity (the ratio of kcat/Km of MMP-7 with incubation to that without it), while CS decreased relative activity. These results indicate that heparin increases the activity and stability of MMP-7, while CS decreases them.

Inhibitory Effects of Alcohols on the Activity of Human Matrix Metalloproteinase 7 (Matrilysin)

Aliphatic alcohols inhibited the activity of human matrix metalloproteinase 7 (matrilysin) competitively with K(i) of 6.1-19.4% (v/v) or 0.66-4.80 M. From the relationship between the structures of alcohols and their K(i) values, alcohols are considered to bind the hydrophobic S1' subsite most plausibly, and the size of the pocket was estimated to be large enough to accommodate the length of 1-butanol (4-carbon chain) and the bulk of tertiary alcohols. Alcohols might be suitable probes for exploring the active-site geometry of enzymes.

A possibility of a protein-bound water molecule as the ionizable group responsible for pKe at the alkaline side in human matrix metalloproteinase 7 activity

Human matrix metalloproteinase 7 (MMP-7) activity exhibits broad bell-shaped pH profile with the acidic and alkaline pK(a) (pK(e1) and pK(e2)) values of about 4 and 10. The ionizable group for pK(e2) was assigned to Lys or Arg by thermodynamic analysis; however, no such residues are present in the active site. Hence, based on the crystal structure, we hypothesized that a water molecule bound to the main-chain nitrogen of Ala162 (W1) or the main-chain carbonyl oxygen of Pro217 (W2) is a candidate for the ionizable group for pK(e2) [Takeharu, H. et al. (2011) Biochim. Biophys. Acta 1814, 1940-1946]. In this study, we inspected this hypothesis. In the hydrolysis of (7-methoxycoumarin-4-yl)acetyl-L-Pro-L-Leu-Gly-L-Leu-[N(3)-(2,4-dinitrophenyl)-L-2,3-diaminopropionyl]-L-Ala-L-Arg-NH(2), all 19 variants, in which one of all Lys and Arg residues was replaced by Ala, retained activity, indicating that neither Lys nor Arg is the ionizable group. pK(e2) values of A162S, A162V and A162G were 9.6 ± 0.1, 9.5 ± 0.1 and 10.4 ± 0.2, respectively, different from that of wild-type MMP-7 (WT) (9.9 ± 0.1) by 0.3-0.5 pH unit, and those of P217S, P217V and P217G were 10.1 ± 0.1, 9.8 ± 0.1 and 9.7 ± 0.1, respectively, different from that of WT by 0.1-0.2 pH unit. These results suggest a possibility of W1 or W2 as the ionizable group for pK(e2).

Nitric oxide and metalloproteinases in canine articular ligaments: A comparison between the cranial cruciate, the medial genual collateral and the femoral head ligament

Osteoarthritis due to cranial cruciate ligament (CCL) rupture or hip dysplasia is one of the most important causes of chronic lameness in dogs. This study aimed at comparing nitric oxide (NO) production by the CCL with that of the femoral head ligament (FHL) and the medial collateral ligament (MCL), and investigating the pathway of NO production and the concomitant metalloproteinase (MMP) activity in the presence or absence of an inflammatory stimulus. Ligaments of normal dogs were subjected to different stimuli, and NO and MMP activity from explant culture supernatants were compared. The results showed that in explant cultures of the canine CCL more NO was produced than in those of the other two ligaments. A higher level of NO was produced when CCLs were exposed to the inducible nitric oxide synthase (iNOS)-inducing cocktail TNF/IL-1/LPS, and NO synthesis could be inhibited by both l-NMMA, a general nitric oxide synthase (NOS) inhibitor and l-NIL, a specific iNOS inhibitor. However, a correlation between NO synthesis and iNOS expression levels as determined by immunohistochemistry was not observed. In contrast to CCL, no evidence for iNOS-dependent NO synthesis was observed for MCL and FHL. The CCL produced less MMP than MCL and FHL, and no correlation between MMP and NO could be demonstrated. MMP activity in the CCL increased significantly after 48 h of incubation with the inflammatory stimulus. The results suggest that in canine osteoarthritis NO synthesized by canine CCL plays a more important role in the pathogenesis of osteoarthritis of the stifle than that synthesized by FHL and MCL.

Effects of High Concentration of Salts on the Esterase Activity and Structure of a Kiwifruit Peptidase, Actinidain

Effects of salts on the activity and stability of actinidain were examined. With increasing salt concentration up to 0.5 M, the activity (kcat/Km) for N-alpha-Cbz-L-lysine p-nitrophenyl ester decreased to 40% of that in the absence of salt. The inhibitor constant Ki of LiCl, NaCl, and KCl was 0.16-0.43 M. With 3 M KCl and NaCl, the specificity constant kcat/Km recovered to 110 and 75%, respectively. No re-activation was observed with LiCl. The inhibition and re-activation were dependent on the changes in both Km and kcat, whereas no CD change was observed. The tryptophan fluorescence of actinidain was not affected by 0-0.5 M salt, but a considerable decrease in its intensity was observed with increasing salt concentration from 0.5 to 3.0 M. These results suggest that the inhibition observed with the lower salt concentration (<0.5 M) is due to attenuation of the electrostatic interaction between the enzyme and substrate, and the higher concentration (0.5-3.0 M) induces structural change in the states of tryptophan residues, which is associated with the re-activation. Actinidain keeps considerably high activity and stability even in the presence of 3 M salts.

Anomalous pH-dependence of the activity of human matrilysin (matrix metalloproteinase-7) as revealed by nitration and amination of its tyrosine residues

Matrilysin activity exhibits a broad bell-shaped pH-dependence profile, with pK(a) values of 4.0 and 9.8. A maximum of five out of eight tyrosine residues in matrilysin were nitrated with tetranitromethane. On nitration of between one and five tyrosines, pK(a) at the alkaline side (pK(e2)) was shifted from 9.8 to 10.3-10.6, while that at the acidic side (pK(e1)) was not altered. The pK(e2) that was shifted by nitration to 10.3-10.6 was restored to 9.4-9.7 by subsequent amination, suggesting that the shift in pK(e2) is induced by a negative charge introduced on the most reactive tyrosine, Tyr-150. The Michaelis constant (K(m)) observed at pH 10 was decreased by nitration as a result of the increase in pK(e2), suggesting that the residue with pK(e2) may play a role in the recognition of substrate. When four or five tyrosines were nitrated, the activity at pH <7 decreased significantly, while that at pH 7-10 was unchanged, and thus the pH-dependence was not bell-shaped, but anomalous, with a third pK(a) (pK(e3)) of 6.2-6.4 in addition to pK(e1) and pK(e2). This suggests the possibility that a newly introduced nitrotyrosine residue has a strong influence on the activity as an ionizable group.

Inhibitory effects of lignans on the activity of human matrix metalloproteinase 7 (matrilysin)

Inhibitory effects of nine dibenzylbutyrolactone lignans on a human matrix metalloproteinase, matrilysin, were examined. All of the lignans examined inhibited matrilysin with the IC(50) values ranging from 50 to >280 microM. Matairesinol, which has the basic structure of the other lignans, showed the weakest inhibition. Lignans with methylenedioxy ring(s) or a hydroxyl group at the C5-position inhibited matrilysin more strongly than matairesinol. 5-Hydroxypluviatolide, which has both a methylenedioxy ring and a hydroxyl group at the C5-position, was the most potent inhibitor (IC(50) = 50 microM), suggesting that the introduction of these two elements might enhance synergistically the inhibitory activity of lignans. 5-Hydroxypluviatolide inhibited matrilysin in a competitive manner, and its inhibitory effect was greatly suppressed by the presence of another competitive inhibitor, dimethyl sulfoxide. The precursors of matairesinol, coniferyl alcohol and secoisolariciresinol, had no inhibitory activity, indicating that the dibenzylbutyrolactone structure is essential for the inhibition. It has been shown that lignans have the potential to inhibit matrilysin, and the knowledge of their structure-activity relationship might be beneficial to developing selective inhibitors for matrix metalloproteinases.

Characterization of Mca-Lys-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2, a fluorogenic substrate with increased specificity constants for collagenases and tumor necrosis factor converting enzyme

Matrix metalloproteinases (MMPs) and the related tumor necrosis factor converting enzyme (TACE) are involved in tissue remodeling, cell migration, and processing of signaling molecules, such as cytokines and adhesion molecules. Fluorescence-quenched peptide substrates have been widely used to quantitate the actual enzymatic activity of MMPs. However, the various MMPs have very different specific activities toward these substrates. This restricts their value for the determination of composite proteolytic activity of mixtures of metalloproteinases in biological fluids. The N-terminal elongation of the most widely used MMP substrate (FS-1) with a Lys to the sequence Mca-Lys-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH(2) (FS-6) yields a fluorogenic peptide with improved substrate properties. As compared to FS-1, the specificity constant (kcat/Km) of FS-6 for collagenases (MMP-1, MMP-8, MMP-13) and MT1-MMP (MMP-14) is increased two- to ninefold and threefold, respectively, while those for gelatinases and matrilysin remain equally high. Using high-performance liquid chromatography-fluorescence detection, MMP activity can be quantitated in the picomolar range. FS-6 shows up to twofold higher specificity constants (kcat/Km of 0.8x10(6)M(-1)s(-1)) for TACE, as compared to standard substrates Mca-PLAQAV-Dpa-RSSSAR-NH(2) and Dabcyl-LAQAVRSSSAR-EDANS. FS-6 is fully water soluble and thus allows measurement of metalloproteinase activity in tissue culture conditions, e.g., on the surface of viable cells in situ.