Disease variants of human Δ1-pyrroline-5-carboxylate reductase 2 (PYCR2)

Sagar M. Patel, Javier Seravalli, Xinwen Liang, John J. Tanner, Donald F. Becker

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Pyrroline-5-carboxylate reductase (PYCR in humans) catalyzes the final step of L-proline biosynthesis by catalyzing the reduction of L-Δ1-pyrroline-5-carboxylate (L-P5C) to L-proline using NAD(P)H as the hydride donor. In humans, three isoforms PYCR1, PYCR2, and PYCR3 are known. Recent genome-wide association and clinical studies have revealed that homozygous mutations in human PYCR2 lead to postnatal microcephaly and hypomyelination, including hypomyelinating leukodystrophy type 10. To uncover biochemical and structural insights into human PYCR2, we characterized the steady-state kinetics of the wild-type enzyme along with two protein variants, Arg119Cys and Arg251Cys, that were previously identified in patients with microcephaly and hypomyelination. Kinetic measurements with PYCR2 suggest a sequential binding mechanism with L-P5C binding before NAD(P)H and NAD(P)+ releasing before L-Pro. Both disease-related variants are catalytically impaired. Depending on whether NADPH or NADH was used, the catalytic efficiency of the R119C protein variant was 40 or 366 times lower than that of the wild-type enzyme, while the catalytic efficiency of the R251C protein variant was 7 or 26 times lower than that of the wild-type enzyme. In addition, thermostability and circular dichroism measurements suggest that the R251C protein variant has a pronounced folding defect. These results are consistent with the involvement of Arg119Cys and Arg251Cys in disease pathology.

Original languageEnglish (US)
Article number108852
JournalArchives of Biochemistry and Biophysics
StatePublished - May 30 2021


  • Circular dichroism
  • Product inhibition kinetics
  • Proline biosynthesis
  • Protein thermostability
  • Steady-state kinetics
  • Substrate-binding order
  • Δ-pyrroline-5-carboxylate reductase

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology


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