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Purification of Urease from Pleurotus sajor-caju.
Characterisation of GTPase Activity of UreG and
Biochemical Properties of the enzyme
Antik K. Bose
ABSTRACT
Biochemical properties of urease obtained from fruiting body extract of Pleurotus sajor-
caju have been described. The enzyme was purified 3176.623 fold by CM-cellulose, DEAE-
cellulose and Sephadex G-200 column chromatography. The molar mass estimated by
Sephadex G-200 was 510KD and saccharide content was 4%. 6% SDS-PAGE of purified
urease showed subunits UreA/B homodimer (28.8 KD ), UreC (150 KD), UreD (104 KD),
UreE (21.5 KD), UreF (102 KD) and UreG (103KD). GTPase activity of UreG was
characterized with KM, Vmax & Kcat to be 2.6mM, 1.1µ mol GTP hydrolyzed/ min and 0.27
min-1
. The enzyme hydrolyzed urea with KM and Vmax to be 1.85mM and 64.51 µ mol NH3
C and 7.4 respectively. The enzyme
activity was enhanced by Ca
2+
(2.94%), 5-10 mM, Mn
2+
( 2.67-52.406%), 20-50mM Ni
2+
(2.6-6.93% ) and 5-10mM Mncl2 ( 0.58- 8.02% ). The enzyme showed product inhibition by
NH4
+
. Competitive inhibition by thiourea and uncompetitive inhibition by NaF were also
studied. Amino acids at the active site have been identified to be Histidine and Aspartic
acid using DEPC and Diazomethane with EDAC