In enzymology, a 1-aminocyclopropane-1-carboxylate deaminase (EC 3.5.99.7) is an enzyme that catalyzes the chemical reaction

1-aminocyclopropane-1-carboxylate + H₂O ${\displaystyle \rightleftharpoons }$ 2-oxobutanoate + NH₃

Thus, the two substrates of this enzyme are 1-aminocyclopropane-1-carboxylate and H₂O, whereas its two products are 2-oxobutanoate and NH₃.

This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in compounds that have not been otherwise categorized within EC number 3.5. The systematic name of this enzyme class is 1-aminocyclopropane-1-carboxylate aminohydrolase (isomerizing). This enzyme is also called 1-aminocyclopropane-1-carboxylate endolyase (deaminating). This enzyme participates in propanoate metabolism. It employs one cofactor, pyridoxal phosphate.

As of late 2007, 6 structures have been solved for this class of enzymes, with PDB accession codes 1RQX, 1TYZ, 1TZ2, 1TZJ, 1TZK, and 1TZM.

• Honma M, Shimomura T (1978). "Metabolism of 1-aminocyclopropane-1-carboxylic acid". Agric. Biol. Chem. 42 (10): 1825–1831. doi:10.1271/bbb1961.42.1825.
• Wakatsuki S, Yokoi D, Murakami T, Honma M, Tanaka I (2000). "Crystal structure of 1-aminocyclopropane-1-carboxylate deaminase from Hansenula saturnus". J. Biol. Chem. 275 (44): 34557–34565. doi:10.1074/jbc.M004681200. PMID 10938279.