Hydrogen Bond Residue Positioning in the 599–611 Loop of Thimet Oligopeptidase is Required for Substrate Selection

SMC Author

Jeffrey Sigman

SMC Affiliated Work

1

Status

Faculty

School

School of Science

Department

Chemistry

Document Type

Article

Publication Date

2008

Publication / Conference / Sponsorship

The FEBS Journal

Description/Abstract

Thimet oligopeptidase (EC 3.4.24.15) is a zinc(II) endopeptidase implicated in the processing of numerous physiological peptides. Although its role in selecting and processing peptides is not fully understood, it is believed that flexible loop regions lining the substrate‐binding site allow the enzyme to conform to substrates of varying structure. This study describes mutant forms of thimet oligopeptidase in which Gly or Tyr residues in the 599–611 loop region were replaced, individually and in combination, to elucidate the mechanism of substrate selection by this enzyme. Decreases in kcatobserved on mutation of Tyr605 and Tyr612 demonstrate that these residues contribute to the efficient cleavage of most substrates. Modeling studies showing that a hinge‐bend movement brings both Tyr612 and Tyr605 within hydrogen bond distance of the cleaved peptide bond supports this role. Thus, molecular modeling studies support a key role in transition state stabilization of this enzyme by Tyr605. Interestingly, kinetic parameters show that a bradykinin derivative is processed distinctly from the other substrates tested, suggesting that an alternative catalytic mechanism may be employed for this particular substrate. The data demonstrate that neither Tyr605 nor Tyr612 is necessary for the hydrolysis of this substrate. Relative to other substrates, the bradykinin derivative is also unaffected by Gly mutations in the loop. This distinction suggests that the role of Gly residues in the loop is to properly orientate these Tyr residues in order to accommodate varying substrate structures. This also opens up the possibility that certain substrates may be cleaved by an open form of the enzyme.

Keywords

enzyme flexibility, hydrogen bonding, metallopeptidase, substrate selectivity, thimet oligopeptidase

Scholarly

yes

DOI

10.1111/j.1742-4658.2008.06685.x

Volume

275

Issue

22

First Page

5607

Last Page

5617

Disciplines

Chemistry

Rights

Open Access article

Original Citation

Bruce L, Sigman JA, Randall D, Rodriguez S, Song M, Dai A, Elmore D, Pabon A, Glucksman MJ, Wolfson, AJ. (2008). Hydrogen bond residue positioning in the 599–611 loop of thimet oligopeptidase is required for substrate selection. The FEBS Journal. 275(22): 5607-17. (2008) https://doi.org/10.1111/j.1742-4658.2008.06685.x

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