Identification of cytidine-5-triphosphate synthase1-selective inhibitory peptide from random peptide library displayed on T7 phage

Peptides. 2017 Aug;94:56-63. doi: 10.1016/j.peptides.2017.06.007. Epub 2017 Jul 1.


Cytidine triphosphate synthase 1 (CTPS1) is an enzyme expressed in activated lymphocytes that catalyzes the conversion of uridine triphosphate (UTP) to cytidine triphosphate (CTP) with ATP-dependent amination, using either L-glutamine or ammonia as the nitrogen source. Since CTP plays an important role in DNA/RNA synthesis, phospholipid synthesis, and protein sialyation, CTPS1-inhibition is expected to control lymphocyte proliferation and size expansion in inflammatory diseases. In contrast, CTPS2, an isozyme of CTPS1 possessing 74% amino acid sequence homology, is expressed in normal lymphocytes. Thus, CTPS1-selective inhibition is important to avoid undesirable side effects. Here, we report the discovery of CTpep-3: Ac-FRLGLLKAFRRLF-OH from random peptide libraries displayed on T7 phage, which exhibited CTPS1-selective binding with a KD value of 210nM in SPR analysis and CTPS1-selective inhibition with an IC50 value of 110nM in the enzyme assay. Furthermore, two fundamentally different approaches, enzyme inhibition assay and HDX-MS, provided the same conclusion that CTpep-3 acts by binding to the amidoligase (ALase) domain on CTPS1. To our knowledge, CTpep-3 is the first CTPS1-selective inhibitor.

Keywords: CTPS1; HDX-MS; Peptide; Phage display.

MeSH terms

  • Bacteriophage T7 / metabolism*
  • Carbon-Nitrogen Ligases / antagonists & inhibitors*
  • Humans
  • Lymphocytes / drug effects
  • Lymphocytes / enzymology*
  • Peptide Library
  • Peptides / pharmacology*


  • Peptide Library
  • Peptides
  • Carbon-Nitrogen Ligases
  • CTP synthetase