Alanine racemase from the acidophile Acetobacter aceti.
Acetobacter aceti converts ethanol to acetic acid, and survives acetic acid exposure by tolerating cytoplasmic acidification. Alanine racemase (Alr) is a pyridoxal 5' phosphate (PLP) -dependent enzyme that catalyzes the interconversion of the d- and l-isomers of alanine and has a basic pH optimum. Since d-alanine is essential for peptidoglycan biosynthesis, Alr must somehow function in the acidic cytoplasm of A. aceti. We report the partial purification of native A. aceti Alr (AaAlr) and evidence that it is a rather stable enzyme. The C-terminus of AaAlr has a strong resemblance to the ssrA-encoded protein degradation signal, which thwarted initial protein expression experiments. High-activity AaAlr forms lacking a protease recognition sequence were expressed in Escherichia coli and purified. Biophysical and enzymological experiments confirm that AaAlr is intrinsically acid-resistant, yet has the catalytic properties of an ordinary Alr.
Francois
Julie A
JA
Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
Kappock
T Joseph
TJ
D000091:Acetobacter / Q000201:enzymology*; D000411:Alanine Racemase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification
D011993:Recombinant Fusion Proteins; D000411:Alanine Racemase