The Active Site of a Zinc-Dependent Metalloproteinase Influences the Computed pK a of Ligands Coordinated to the Catalytic Zinc Ion

• Published in: Journal of the American Chemical Society Vol. 124; no. 37; pp. 11004 - 11007
• Main Authors: Cross, Jason B, Duca, José S, Kaminski, James J, Madison, Vincent S
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 18.09.2002
• Subjects: ADAM Proteins; ADAM17 Protein; Binding Sites; Cations; Enzyme Inhibitors - chemistry; Enzyme Inhibitors - metabolism; Hydroxamic Acids - chemistry; Hydroxamic Acids - metabolism; Kinetics; Ligands; Metalloendopeptidases - antagonists & inhibitors; Metalloendopeptidases - chemistry; Metalloendopeptidases - metabolism; Models, Molecular; Thermodynamics; Zinc - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0201810

TNF-α 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-α (TNF-α) from its membrane-bound precursor. TACE is a metalloprotease containing a catalytic glutamic acid, Glu-406, and a Zn2+ 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.