The active site of a zinc-dependent metalloproteinase influences the computed pK(a) of ligands coordinated to the catalytic zinc ion.
TNF-alpha converting enzyme (TACE) is a multidomain, membrane-anchored protein that includes a Zn-dependent protease domain. It releases the soluble form of cytokine tumor necrosis factor-alpha (TNF-alpha) from its membrane-bound precursor. TACE is a metalloprotease containing a catalytic glutamic acid, Glu-406, and a Zn(2+) ion ligated to three imidazoles. The protonation states of the active site glutamic acid and inhibitors are important factors in understanding the potency of inhibitors with acidic zinc-ligating groups such as hydroxamic and carboxylic acids. Density functional methods were utilized to compute pK(a) values using a model of the catalytic site of TACE and to predict a concomitant mechanism of binding, consistent with lowering the pK(a) of the bound ligand and raising the pK(a) of the active site Glu-406. Weak acids, such as hydroxamic acids, bind in their neutral form and then transfer an acidic proton to Glu-406. Stronger acids, such as carboxylic acids, bind in their anionic form and require preprotonation of Glu-406. Similar binding events would be expected for other zinc-dependent proteases.
Cross
Jason B
JB
Contribution from the Department of Structural Chemistry, Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033, USA.
Duca
José S
JS
Kaminski
James J
JJ
Madison
Vincent S
VS
D051722:ADAM Proteins; D000072198:ADAM17 Protein; D001665:Binding Sites; D002412:Cations; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism; D006877:Hydroxamic Acids / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D013816:Thermodynamics; D015032:Zinc / Q000737:chemistry*
D002412:Cations; D004791:Enzyme Inhibitors; D006877:Hydroxamic Acids; D008024:Ligands; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000072198:ADAM17 Protein; D015032:Zinc