Substrate specificity of platypus venom L-to-D-peptide isomerase

Bansal, Paramjit S., Torres, Allan M., Crossette, Ben, Wong, Karen K.Y., Koh, Jennifer M.S., Geraghty, Dominic P., Vandenberg, Jamie I., and Kuchel, Philip W. (2008) Substrate specificity of platypus venom L-to-D-peptide isomerase. Journal of Biological Chemistry, 283 (14). pp. 8969-8975.

[img] PDF (Published Version) - Published Version
Restricted to Repository staff only

View at Publisher Website: http://dx.doi.org/10.1074/jbc.M709762200
 
42
1


Abstract

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, alpha-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, beta-branched or long side chains with polar terminal groups, viz. Ala, alpha-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.

Item ID: 32522
Item Type: Article (Research - C1)
ISSN: 1083-351X
Funders: Australian Research Council (ARC)
Date Deposited: 25 Aug 2014 06:25
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1101 Medical Biochemistry and Metabolomics > 110101 Medical Biochemistry: Amino Acids and Metabolites @ 100%
SEO Codes: 92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920407 Health Protection and/or Disaster Response @ 100%
Downloads: Total: 1
More Statistics

Actions (Repository Staff Only)

Item Control Page Item Control Page