Mechanism of the binding of Z-L-tryptophan and Z-L-phenylalanine to thermolysin and stromelysin-1 in aqueous solutions.
The chemical shift of the carboxylate carbon of Z-tryptophan is increased from 179.85 to 182.82 ppm and 182.87 ppm on binding to thermolysin and stromelysin-1 respectively. The chemical shift of Z-phenylalanine is also increased from 179.5 ppm to 182.9 ppm on binding to thermolysin. From pH studies we conclude that the pK(a) of the inhibitor carboxylate group is lowered by at least 1.5 pK(a) units when it binds to either enzyme. The signal at ~183 ppm is no longer observed when the active site zinc atom of thermolysin or stromelysin-1 is replaced by cobalt. We estimate that the distance of the carboxylate carbon of Z-[1-(13)C]-L-tryptophan is ≤3.71Å from the active site cobalt atom of thermolysin. We conclude that the side chain of Z-[1-(13)C]-L-tryptophan is not bound in the S(2)' subsite of thermolysin. As the chemical shifts of the carboxylate carbons of the bound inhibitors are all ~183 ppm we conclude that they are all bound in a similar way most probably with the inhibitor carboxylate group directly coordinated to the active site zinc atom. Our spectrophotometric results confirm that the active site zinc atom is tetrahedrally coordinated when the inhibitors Z-tryptophan or Z-phenylalanine are bound to thermolysin.
UCD School Biomelocular and Biomedical Science, UCD Centre for Synthesi and Chemical Biology, SEC Strategic Research Cluster, Conway Institute, University College Dublin, Dublin, Ireland.
Mariangela
M
Ceruso
Nicole
N
Howe
J Paul G
JP
Malthouse
D001665:Binding Sites; D020134:Catalytic Domain / Q000502:physiology; D003035:Cobalt / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D019278:Matrix Metalloproteinase 3 / Q000737:chemistry*; D061965:Matrix Metalloproteinase Inhibitors; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry; D011480:Protease Inhibitors / Q000737:chemistry*; D011487:Protein Conformation; D012996:Solutions; D013820:Thermolysin / Q000037:antagonists & inhibitors / Q000737:chemistry*; D014364:Tryptophan / Q000031:analogs & derivatives* / Q000737:chemistry; D014867:Water / Q000737:chemistry; D015032:Zinc / Q000378:metabolism
D061965:Matrix Metalloproteinase Inhibitors; D011480:Protease Inhibitors; D012996:Solutions; D014867:Water; C017105:carbobenzoxyphenylalanine; D003035:Cobalt; D010649:Phenylalanine; C045552:benzyloxycarbonyltryptophan; D014364:Tryptophan; D019278:Matrix Metalloproteinase 3; D013820:Thermolysin; D015032:Zinc