<Emphasis Type="SmallCaps">d</Emphasis>-Amino Acids in Animal Peptides |
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Authors: | Alexander Jilek Günther Kreil |
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Institution: | (1) Institute of Organic Chemistry, Johannes Kepler University Linz, Linz, Austria;(2) Institute of Physiology and Pathophysiology, Paracelsus Medical University, Salzburg, Austria |
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Abstract: | Summary. Secreted peptides from diverse sources have been found to contain a d-amino acid. From the sequence of cloned mRNAs coding for the precursors of such peptides it could be deduced that in all cases tested so far the d-amino acid in the final product is derived from the corresponding l-amino acid present in the primary product of translation. Enzymes catalyzing such an l- to d-isomerization in peptide linkage have been isolated from the venom of a spider and the skin secretions of frogs. Even though
these are completely different proteins, the reaction mechanism is the same, namely a de-protonation/re-protonation of the
α-carbon of an amino acid with concomitant inversion of the chirality. Sequences potentially coding for homologues of the
frog enzyme are present in the genome of different vertebrate species. |
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Keywords: | , Peptides, Enantiomerization, Isomerase, Chiral inversion, |
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