# proline

> English word · Noun · frequency rank #56,381

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

## Etymology
Short for pyrrolidine.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/proline