Analysis of enzymatic L/D-peptide isomerization in animals

Tai, Hua-Chia

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https://hdl.handle.net/2142/101796 Copy

Description

Title

Analysis of enzymatic L/D-peptide isomerization in animals

Author(s)

Tai, Hua-Chia

Issue Date

2018-07-10

Director of Research (if dissertation) or Advisor (if thesis)

Sweedler, Jonathan V.

Doctoral Committee Chair(s)

Sweedler, Jonathan V.

Committee Member(s)

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

Department of Study

Molecular & Integrative Physl

Discipline

Molecular & Integrative Physi

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

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

Abstract

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.

Graduation Semester

2018-08

Type of Resource

text

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Copyright and License Information

Copyright 2018 Hua-Chia Tai

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