تنقية و توصيف أنزيم بيتا-كالاكتوسيديز المنتج من عزلة محلية من العفن الآلف للحرارة العالية Rhizomucor pusillus IB8

الملخص EN

An extracellular p-galactosidase from the thermophilic fungus Rhizomucor Pusillus IB8 has been purified via several steps included precipitation by ammonium sulphate at 80 % saturation, DEAE- Cellulose Ion exchange chromatography and gel filteration on sepharose CL-6B column.

The Final purification folds and the yield of the enzyme were 42.5 and 24.8 % respectively.

The purified p-galactosidase has an optimum pH for its activity between 4.5 to 5, while the optimum pH for enzyme stability was between 5 to 5.5.

Futhermore, it was found that the optimum temperature for its activity was 60 C°.

The purified enzyme retained approximatly 98% of its original activity when incubated at 60 C° for 60 min.

However, 25 % of its activity was lost when incubated for 120 min at the same tmperaure.

Activation energy for conversion of the substrate ONPG to products was 6.15 Kcal / mol, whereas, for enzyme denaturation it was 99.3 Kcal / mol.

The molecular weight of the purified enzyme was 232000 dalton as determined by gel filtration on sepharose CL-6B.

Kinetic studies showed that the Michaelis constant (Km) and maximum velocity (Vmax) values for the purified enzyme using ONPG as a substrate were 0.46 mM and 223 ^M /min respectively.