HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 283, Issue 14, 8969-8975, April 4, 2008

This Article Full Text Full Text (PDF) All Versions of this Article: 283/14/8969    most recent M709762200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Bansal, P. S. Articles by Kuchel, P. W. Search for Related Content PubMed PubMed Citation Articles by Bansal, P. S. Articles by Kuchel, P. W. Social Bookmarking                      What's this?

Substrate Specificity of Platypus Venom L-to-D-Peptide Isomerase^*

Paramjit S. Bansal, Allan M. Torres, Ben Crossett, Karen K. Y. Wong, Jennifer M. S. Koh, Dominic P. Geraghty^¶, Jamie I. Vandenberg^||, and Philip W. Kuchel¹

From the School of Molecular and Microbial Biosciences, University of Sydney, New South Wales 2006, Nanoscale Organisation and Dynamics Group, College of Health and Science, University of Western Sydney, Penrith South DC, New South Wales 1797, ^¶School of Human Life Sciences, University of Tasmania, Launceston, Tasmania 7250, and ^||Mark Cowley Lidwill Cardiac Electrophysiology and Biophysics Program, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia

The L-to-D-peptide isomerase from the venom of the platypus (Ornithorhyncus anatinus) is the first such enzyme to be reported for a mammal. In delineating its catalytic mechanism and broader roles in the animal, its substrate specificity was explored. We used N-terminal segments of defensin-like peptides DLP-2 and DLP-4 and natriuretic peptide OvCNP from the venom as substrates. The DLP analogues IMFsrs and ImFsrs (srs is a solubilizing chain; lowercase letters denote D-amino acid) were effective substrates for the isomerase; it appears to recognize the N-terminal tripeptide sequence Ile-Xaa-Phe-. A suite of 26 mutants of these hexapeptides was synthesized by replacing the second residue (Met) with another amino acid, viz. Ala, -aminobutyric acid, Ile, Leu, Lys, norleucine, Phe, Tyr, and Val. It was shown that mutant peptides incorporating norleucine and Phe are substrates and exhibit L- or D-amino acid isomerization, but mutant peptides that contain residues with shorter, β-branched or long side chains with polar terminal groups, viz. Ala, -aminobutyric acid, Ile, Val, Leu, Lys, and Tyr, respectively, are not substrates. It was demonstrated that at least three N-terminal amino acid residues are absolutely essential for L- to D-isomerization; furthermore, the third amino acid must be a Phe residue. None of the hexapeptides based on LLH, the first three residues of OvCNP, were substrates. A consistent 2-base mechanism is proposed for the isomerization; abstraction of a proton by 1 base is concomitant with delivery of a proton by the conjugate acid of a second base.

Received for publication, November 29, 2007

^* This work was supported by an Australian Research Council Discovery Project grant awarded (to P. W. K. and J. I. V.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: School of Molecular and Microbial Biosciences, Bldg. G08, University of Sydney, New South Wales 2006, Australia. Tel.: 61-2-9351-3709; Fax: 61-2-9351-4726; E-mail: p.kuchel{at}mmb.usyd.edu.au.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?