Metabolism of 1-aminocyclopropane-1-carboxylic acid.

Several microorganisms capable of utilizing 1-aminocyclopropane-l-carboxylate (ACPC) were isolated from soil. A bacterium which belongs to Pseudomonas accumulated cellular a-aminobutyrate with consumption of ACPC and cells incubated with ACPC medium had the activity deaminating the substrate to form α-ketobutyrate. An enzyme, ACPC deaminase, was highly purified and its molecular weight, substrate specificity and absorption spectrum were investigated. These results suggested that this enzyme was a pyridoxal 5'-phosphate enzyme which has the molecular weight of 104000 and high specificity for ACPC, Km=1.5mM. A yeast, Hansenula saturnus, is also capable of forming ACPC deaminase, which has a lower molecular weight, 69000, and higher Km value, 2.6mM.