The major component of the enzyme’s secondary structure was
determined to be a-helical by circular dichroism (CD). P. putida UW4 ACCD unfolded at 60 8C as determined by its CD temperature profile
as well as by differential scanning microcalorimetry (DSC). Enzyme activity was knocked out in the point mutant Gly44Asp. Modeling this
mutation into the known yeast ACCD structure shed light on the role this highly conserved residue plays in allowing substrate accessibility to
the active site. This enzyme’s biochemical and biophysical properties will serve as an important reference point to which newly isolated ACC
deaminases from other organisms can be compared.