Hydroxyproline vs. Proline — What's the Difference?

(2S,4R)-4-Hydroxyproline, or L-hydroxyproline (C5H9O3N), is an amino acid, abbreviated as Hyp or O, e.g., in Protein Data Bank.

Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group -NH2 but is rather a secondary amine. The secondary amine nitrogen is in the protonated NH2+ form under biological conditions, while the carboxy group is in the deprotonated −COO− form.

(biochemistry) A hydroxy derivative of the amino acid proline found in the structural proteins of connective tissue

An amino acid, C5H9NO2, that is found in most proteins and is a major constituent of collagen.

A crystalline amino acid (C5H9NO3), a hydroxylated proline, obtained by hydrolysis of gelatin or collagen. Chemically it is 4-hydroxy-L-proline. It is classified as nonessential for growth in rats.

(amino acid) A nonessential amino acid C₅H₉NO₂ found in most animal proteins, especially collagen; its cyclic structure leads to kinks in the peptide chain of proteins.

A crystalline amino acid obtained from gelatin or collagen

An amino acid that is found in many proteins (especially collagen)