In enzymology, a proline—tRNA ligase (EC 22.214.171.124) is an enzyme that catalyzes the chemical reaction
- ATP + L-proline + tRNAPro AMP + diphosphate + L-prolyl-tRNAPro
The 3 substrates of this enzyme are ATP, L-proline, and tRNA(Pro), whereas its 3 products are AMP, diphosphate, and L-prolyl-tRNA(Pro).
This enzyme belongs to the family of ligases, to be specific those forming carbon-oxygen bonds in aminoacyl-tRNA and related compounds. The systematic name of this enzyme class is L-proline:tRNAPro ligase (AMP-forming). Other names in common use include prolyl-tRNA synthetase, prolyl-transferRNA synthetase, prolyl-transfer ribonucleate synthetase, proline translase, prolyl-transfer ribonucleic acid synthetase, prolyl-s-RNA synthetase, and prolinyl-tRNA ligase. This enzyme participates in arginine and proline metabolism and aminoacyl-trna biosynthesis.
Structural studies 
As of late 2007, 15 structures have been solved for this class of enzymes, with PDB accession codes 1H4Q, 1H4S, 1H4T, 1HC7, 1NJ1, 1NJ2, 1NJ5, 1NJ6, 1NJ8, 2I4L, 2I4M, 2I4N, 2I4O, 2J3L, and 2J3M.
- Norton SJ (1964). "Purification and properties of the prolyl RNA synthetase of Escherichia coli". Arch. Biochem. Biophys. 106: 147–152. doi:10.1016/0003-9861(64)90167-5. PMID 14217147.
- Peterson PJ and Fowden L (1965). "Purification, properties and comparative specificities of the enzyme prolyl-transfer ribonucleic acid synthetase from Phaseolus aureus and Polygonatum multiflorum". Biochem. J. 97: 112–124. PMID 16749091.