Reaction: 1-aminocyclopropane-1-carboxylate + H2O = 2-oxobutanoate + NH3 (overall reaction)
(1a) 1-aminocyclopropane-1-carboxylate = 2-aminobut-2-enoate
(1b) 2-aminobut-2-enoate = 2-iminobutanoate (spontaneous)
(1c) 2-iminobutanoate + H2O = 2-oxobutanoate + NH3 (spontaneous)
Other name(s): 1-aminocyclopropane-1-carboxylate endolyase (deaminating); ACC deaminase; 1-aminocyclopropane carboxylic acid deaminase
Systematic name: 1-aminocyclopropane-1-carboxylate aminohydrolase (isomerizing)
Comments: A pyridoxal 5'-phosphate enzyme. The enzyme, found in certain soil bacteria and fungi, catalyses the ring opening of 1-aminocyclopropane-1-carboxylate, the immediate precursor to ethylene, an important plant hormone that regulates fruit ripening and other processes. The enzyme releases an unstable enamine product that tautomerizes to an imine form, which undergoes a hydrolytic deamination. The latter reaction, which can occur spontaneously, can also be catalysed by EC 3.5.99.10, 2-iminobutanoate/2-iminopropanoate deaminase. The enzyme has been used to make fruit ripening dependent on externally added ethylene, as it removes the substrate for endogenous ethylene formation.
Links to other databases: BRENDA, EAWAG-BBD, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 69553-48-6
References:
1. Honma, M. and Shimomura, T. Metabolism of 1-aminocyclopropane-1-carboxylic acid. Agric. Biol. Chem. 42 (1978) 1825-1831.
2. Yao, M., Ose, T., Sugimoto, H., Horiuchi, A., Nakagawa, A., Wakatsuki, S., Yokoi, D., Murakami, T., Honma, M. and Tanaka, I. Crystal structure of 1-aminocyclopropane-1-carboxylate deaminase from Hansenula saturnus. J. Biol. Chem. 275 (2000) 34557-34565. [PMID: 10938279]
3. Thibodeaux, C.J. and Liu, H.W. Mechanistic studies of 1-aminocyclopropane-1-carboxylate deaminase: characterization of an unusual pyridoxal 5'-phosphate-dependent reaction. Biochemistry 50 (2011) 1950-1962. [PMID: 21244019]