A non-proteinogenic L-alpha-amino acid that is L-alanine in which one of the methyl hydrogens has been replaced by an ethynyl group. It causes the irreversible inactivation of gamma-cystathionase (also known as cystathionine gamma-lyase) and is used as an affinity labeling reagent for gamma-cystathionase and other enzymes. ChEBI: L-propargylglycine is a non-proteinogenic L-alpha-amino acid that is L-alanine in which one of the methyl hydrogens has been replaced by an ethynyl group. It causes the irreversible inactivation of gamma-cystathionase (also known as cystathionine gamma-lyase) and is used as an affinity labeling reagent for gamma-cystathionase and other enzymes. It has a role as an EC 1.4.3.2 (L-amino-acid oxidase) inhibitor, an EC 2.6.1.2 (alanine transaminase) inhibitor and an EC 2.5.1.48 (cystathionine gamma-synthase) inhibitor. It is a non-proteinogenic L-alpha-amino acid and a terminal acetylenic compound. It is a tautomer of a L-propargylglycine zwitterion.