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Title: Thermodynamic analysis of ionizable groups involved in the catalytic mechanism of human matrix metalloproteinase 7 (MMP-7).
Authors: Takeharu, Hitoshi
Yasukawa, Kiyoshi  kyouindb  KAKEN_id
Inouye, Kuniyo
Author's alias: 井上, 國世
Keywords: Ionizable group
Matrix metalloproteinase
Proton dissociation constant
Thermodynamic analysis
Issue Date: Dec-2011
Publisher: Elsevier B.V.
Journal title: Biochimica et biophysica acta
Volume: 1814
Issue: 12
Start page: 1940
End page: 1946
Abstract: Human matrix metalloproteinase 7 (MMP-7) exhibits a broad bell-shaped pH-dependence with the acidic and alkaline pK(e) (pK(e1) and pK(e2)) values of about 4 and 10. In this study, we estimated the ionizable groups involved in its catalytic mechanism by thermodynamic analysis. pK(a) of side chains of L-Asp, L-Glu, L-His, L-Cys, L-Tyr, L-Lys, and L-Arg at 25-45°C were determined by the pH titration of amino-acid solutions, from which their enthalpy changes, ∆H°, of deprotonation were calculated. pK(e1) and pK(e2) of MMP-7 at 15-45°C were determined 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), from which ∆H(o) for pK(e1) and pK(e2) was calculated. The ∆H(o) for pK(e1) (-20.6±6.1kJmol(-1)) was similar to that for L-Glu (-23.6±5.8kJmol(-1)), and the ∆H(o) for pK(e2) (89.9±4.0kJmol(-1)) was similar to those for L-Arg (87.6±5.5kJmol(-1)) and L-Lys (70.4±4.4kJmol(-1)). The mutation of the active-site residue Glu198 into Ala completely abolished the activity, suggesting that Glu198 is the ionizable group for pK(e1). On the other hand, no arginine or lysine residues are found in the active site of MMP-7. We proposed a possibility that a protein-bound water is the ionizable group for pK(e2).
Rights: © 2011 Elsevier B.V.
This is not the published version. Please cite only the published version. この論文は出版社版でありません。引用の際には出版社版をご確認ご利用ください。
DOI(Published Version): 10.1016/j.bbapap.2011.07.008
PubMed ID: 21787888
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