Purification and characterization of an acetyl esterase from Aspergillus niger.
Optimized acetyl esterase enzyme production conditions using Aspergillus niger ATCC 10864 in 14-L fermentation jars were determined to be 33 degrees C, 1.5 vvm aeration, and 300 rpm agitation without pH control. The acetyl esterase was purified by precipitation in 60-80% saturation in ammonium sulfate. The pellet was applied directly to a Pharmacia high-load Phenyl Sepharose column for hydrophobic interaction chromatography and purified to homogeneity in two steps. Stability and kinetic characteristics of the acetyl esterase were determined over a pH range of 4.0-7.5 and from 4 to 45 degrees C. At temperatures > 25 degrees C, stability was superior at pH values < 5.0. The temperature activity optimum was 35 degrees C, and the pH optimum was 7.0. The Vmax was determined to be 46,700 U/mg protein, and the Km was 0.023M p-nitrophenyl acetate at pH 6.5 in 0.2M phosphate buffer at 35 degrees C. The mol wt of the enzyme was 35,000 dalton by size-exclusion chromatography and SDS gel electrophoresis. The N-terminal amino acid sequence and the glycosylation composition were also determined.
Department of Microbiology, Colorado State University, Fort Collins 80523.
J
J
Linden
M
M
Samara
S
S
Decker
E
E
Johnson
M
M
Boyer
M
M
Pecs
W
W
Adney
M
M
Himmel
D000115:Acetylesterase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D000595:Amino Acid Sequence; D001234:Aspergillus niger / Q000201:enzymology*; D002240:Carbohydrate Sequence; D004795:Enzyme Stability; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D014990:Xylans / Q000737:chemistry / Q000378:metabolism
D014990:Xylans; D000115:Acetylesterase