Estimation of 1-Aminocyclopropane-1-Carboxylate Deaminase (ACC Deaminase) Activity
For the measurement of ACC deaminase activity, selected isolates were grown overnight in 10 mL of NB medium and thereafter
harvested by centrifugation. The pellet was washed with normal saline and suspended in 7.5 mL of JNFb- medium containing 5
mM of 1-aminocyclopropane-1-carboxylate (ACC). Tubes were incubated at 28oC with shaking (120 rpm) for growth. ACC
served as the sole source of nitrogen in the medium. After 24h of growth, cells were centrifuged at 8000 rpm at 4oC for 10 min.
The pellet was suspended in 1 mL of 0.1M Tris-HCl (pH 7.6) and again centrifuged at 15000 rpm for 15 min. Pellet was collected
and supernatant discarded. The pellet was re-suspended in 600 μL of 0.1 M Tris-HCl (pH 8.5). 30 μL of toluene was added to
the cell suspension and vortexed at higher setting for 30 s. Tube was kept at 4oC for 1h and then centrifuged at 1200 rpm for 10
min at 4oC. The thin layer of toluene was aspirated by micro-pipette gently. Now, the toluenized cells were equally distributed
in two eppendroff tubes. First part was stored at 4oC for protein assay and other part was used for ACC deaminase assay
immediately. 200 L of toluenized cells was transferred in a fresh 1.5 mL microcentrifuge tube and 20 L of 0.5 M ACC was
added to the suspension. It was briefly vortexed and incubated at 30oC for 15 min. 1.0 mL of 0.56 M HCl was added, vortexed
and centrifuged for 10 min at 12000 rpm. Now, 1mL of the supernatant was taken in another tube and 800 L of 0.56 M HCl
was added and vortexed briefly. Thereafter 300 L of 2,4, dinitrophenylhydrazine (2 % w/v) was added to the tube. It was mixed
properly by vortexing and incubated at 30oC for 30 min. 2L of 2M NaOH was added and after mixing absorbance was recorded
at 540 nm. The amount of μmol of α-ketobutyrate produced by this reaction was determined and compared with a standard curve
of α-ketobutyrate ranging between 0.1 and 1.0 μmol. For the purpose of standard curve generation a sock solution of 100 mM α-
ketobutyrate (Sigma-Aldrich Co., USA) was prepared in 0.1M Tris-HCl pH 8.5 and stored at 4oC. Enzyme activity was expressed
as mol/mg protein/h