• Proline shares many properties with the aliphatic group.
  • Proline is formally NOT an amino acid, but an imino acid. Nonetheless, it is called an amino acid
  • Nonpolar.
In plants, proline is synthesized by two pathways:

  • Glutamate pathway.:The biosynthetic enzymes (P5CS1, P5CS2 and P5CR) are predicted to be localized in the cytosol 
  • Ornithine pathway.
  • Image result for proline synthesis GLUTAMATE pathway


  • Proline catabolism occurs in mitochondria by some enzymes such as proline dehydrogenase or proline oxidase (PDH or POX) producing P5C from proline and P5C dehydrogenase (P5CDH) which converts P5C to glutamate.
  • Proline catabolism is, therefore, an important regulator of cellular ROS balance and can influence numerous additional regulatory pathways.
  • Proline biosynthesis is important for maintaining NADP+ pools during stress
  • Proline is used for protein synthesis,
  • Purely glucogenic amino acid is proline 
  • Prolinehas protective functions as an osmolyte,
  • Destabilizes alpha-helix 
  • Proline is contributes to the maintenance of the redox balance,
  • Proline can regulate development and is a component of metabolic signaling networks controlling mitochondrial functions, stress relief and development.
  • Reducing oxidation of lipid membranes 
  • Protective proteins and enzymes such as RUBISCO,
  • Scavenging the ROS (free radical scavenger),
  • Buffering cytosolic pH,
  • Balances cell redox status of the cell,
  • A mutation is most likely to alter the three-dimensional conformation of a protein if It places proline in the middle of a α-helix
  • Activates specific gene expression and signaling molecule to modulate mitochondrial functions, and influences cell proliferation or cell death
  • Proline biosynthesis is controlled by the activity of, P5CS is encoded by two genes whereas P5CR is encoded by only one in most plant species
  • Although the duplicated P5CS genes share a high level of sequence homology in coding regions, their transcriptional regulation is different.
  • P5CS1 is induced by osmotic and salt stresses and is activated by an abscisic acid (ABA)-dependent and ABA insensitive 1 (ABI1)-controlled regulatory pathway and H2O2-derived signals.
  • In Proline catabolism there are Two genes encode PDH, whereas a single P5CDH gene has been identified in Arabidopsis and tobacco.
  • PDH transcription is activated by rehydration but repressed by dehydration, thus preventing proline degradation during abiotic stress
Exam Question of :
  • Metabolism of proline takes place in Mitochondria
  • The amino acid residue having an iminoside chain is proline
  • A mutation is most likely to alter the three-dimensional conformation of a protein if It places proline in the middle of a α-helix
  • Amino acid, that destabilizes alpha-helix is proline 
  • Vit C, O2 , Dioxygenases,Fe2+ and α–ketoglutrate are elements required for hydroxylation of proline in collagen synthesis
  • Glutamate is precursor of proline
  • Purely glucogenic amino acid is proline
Don't Forget to Solve all the previous Year Question asked on Proline