Caught after the Act: A Human A-Type Metallocarboxypeptidase in a Product Complex with a Cleaved Hexapeptide

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• 作者：À ; lex Bay&eacute ; s ; Daniel Ferná ; ndez ; Maria Solà ; Aniebrys Marrero ; Sonia Garcí ; a-Piqu&eacute ; Francesc X. Avil&eacute ; s ; Josep Vendrell ; and F. Xavier Gomis-Rü ; th
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：June 12, 2007
• 年：2007
• 卷：46
• 期：23
• 页码：6921 - 6930
• 全文大小：677K
• 年卷期：v.46,no.23(June 12, 2007)
• ISSN：1520-4995

文摘

A/B-type metallocarboxypeptidases (MCPs) are among the most thoroughly studied proteolyticenzymes, and their catalytic mechanisms have been considered as prototypes even for several unrelatedmetalloprote(in)ase families. It has long been postulated that the nature of the side chains of at least fivesubstrate residues, i.e., P₄-P_1', influence K_m and k_cat and that once the peptide or protein substrate iscleaved, both products remain in the first instance bound to the active-site cleft of the enzyme in a double-product complex. Structural details of binding of substrate to the nonprimed side of the cleft have largelyrelied on complexes with protein inhibitors and peptidomimetic small-molecule inhibitors that do notspan the entire groove. In the former, the presence of N-terminal globular protein domains participatingin large-scale interactions with the surface of the cognate catalytic domain outside the active-site cleftmostly conditions the way their C-terminal tails bind to the cleft. Accordingly, they may not be accuratemodels for a product complex. We hereby provide the structural details of a true cleaved double-productcomplex with a hexapeptide of an MCP engaged in prostate cancer, human carboxypeptidase A4, employingdiffraction data to 1.6 Å resolution (R_cryst and R_free = 0.159 and 0.176, respectively). These studies providedetailed information about subsites S₅-S_1' and contribute to our knowledge of the cleavage mechanism,which is revisited in light of these new structural insights.