Purification, characterization, kinetic properties, and thermal behavior of extracellular polygalacturonase produced by filamentous fungus Tetracoccosporium sp |
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Authors: | Saeed Aminzadeh Hossein Naderi-Manesh Khosro Khajeh Mehdi Naderi-Manesh |
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Institution: | (1) Department of Biochemistry and Biophysics, Faculty of Science, Tarbiat Modares University, PO Box 14115-175, Tehran, Iran |
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Abstract: | For the first time, a polygalacturonase from the culture broth of Tetracoccosporium sp. was isolated and incubated at 30°C in an orbital shaker at 160 rpm for 48h. The enzyme was purified by ammonium sulfate
precipitation and two-step ion-exchange chromatography and had an apparent molecular mass of 36 kDa, as shown by sodium dodecyl
sulfate (SDS)-polyacrylamide gel electrophoresis. Its optimum activity was at pH 4.3 and 40°C, and the K
m
and V
max values of this enzyme (for polygalacturonic acid) were 3.23 mg/mL and 0.15 μmol/min, respectively. Ag+, Co2+, EDTA, Tween-20, Tween-80, and Triton X-100 stimulated polygalacturonase activity whereas Al3+, Ba2+, Ca2+, Fe2+, Fe3+, Ni2+, Mg2+, Mn2+, and SDS inhibited it. In addition, iodoacetamide and iodoacetic acid did not inhibit enzyme activity at a concentration
of 1 mM, indicating that cysteine residues are not part of the catalytic site of polygalacturonase. We studied the kinetic properties
and thermal inactivation of polygalacturonase. This enzyme exhibited a t
1/2 of 63 min at 60°C and its specific activity, turnover number, and catalytic efficiency were 6.17 U/mg, 113.64 min−1, and 35.18 mL/(min·mg), respectively. The activation energy (ΔE
#) for heat inactivation was 5.341 kJ/mol, and the thermodynamic activation parameters ΔG
#, ΔH
#, and ΔS
# were also calculated, revealing a potential application for the industry. |
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Keywords: | Polygalacturonase Tetracoccosporium sp kinetic properties thermal stability thermodynamic activation parameters purification |
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