Analysis of enzymatic L/D-peptide isomerization in animals

The study of cell-to-cell signaling peptides contributes to the fundamental understanding of physiological processes and improves the effectiveness of pharmaceutical drugs. While protein synthesis in animals is stereospecific for all L-form amino acids, a unique and bioactive group of D-amino acid-containing peptides (DAACPs) have been found to exist in a broad array of animals. DAACPs result from a post-translational modification (PTM) in which an L-amino acid residue is enzymatically converted into a D-amino acid residue in the peptide chain. Isomerization leads to important changes in the three-dimensional structure and bioactivity of the DAACP and increases its resistance to degradation by peptidases. However, current research into peptide isomerization is limited because this PTM is not easily detected in mass spectrometry-based peptidomics experiments due to the lack of an associated mass shift. To address this challenge, we have developed a method for the non-targeted detection of DAACPs in biological samples and used it to explore the prevalence of DAACPs in the neurobiological model organism Aplysia californica. Two novel DAACPs were discovered using this method. Based on these results, it was hypothesized that an L/D-peptide isomerase exists in Aplysia which is responsible for the biosynthesis of DAACPs. An assay for isomerase activity was developed and used to partially purify and characterize an L/D-isomerase in the Aplysia central nervous system. Furthermore, isomerase activity was detected in multiple tissues in the rat, and a mammalian neuropeptide was found to be isomerized by this activity. These findings advance our understanding of the extent and function of enzymatic L/D-peptide isomerization as a PTM in bioactive peptides.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Molecular & Integrative Physi

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2018

Author dc:creator

• Tai, Hua-Chia

Contributors dc:contributor

• Sweedler, Jonathan V.
• Yau, Peter M.
• Raetzman, Lori T.
• Christian, Catherine A.

• Neuropeptide
• Chirality
• Peptide isomerization
• D-amino acid
• Isomerase
• Mass spectrometry (MS)
• Liquid chromatography-mass spectrometry (LC-MS)

Statement dc:rights

• Copyright 2018 Hua-Chia Tai

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/101796

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/101796