Phytase, also known as phytate-degrading enzyme, catalyzes the hydrolysis of phytate (inositol hexakisphosphate) with sequential release of phosphate and lower inositol phosphate. We report here a new plasmid construc...Phytase, also known as phytate-degrading enzyme, catalyzes the hydrolysis of phytate (inositol hexakisphosphate) with sequential release of phosphate and lower inositol phosphate. We report here a new plasmid construct designated as pMSuia from pBAD-TOPO that harbors a 1.1 kb phytase gene (phyMS) from Mycobacterium smegmatis, and expression as well as characterization of the purified recombinant M. smegmatis phytase. DNA sequencing analysis and multiple alignment exercise indicated that the M. smegmatis phytase is different from both known acid and alkaline phytases. The active ~45 kDa recombinant enzyme was expressed and confirmed by enzyme assay and Western blot analyses. Ni-NTA affinity purified recombinant M. smegmatis phytase exhibited specific activity of 233.51 U/mg, optimal pH of 3 and 7 and optimal temperature of 60°C. The purified enzyme retains almost 30% of the initial activity after incubation at 90°C for 60 min. The enzyme showed broad substrate specificity with Km and Vmax of the recombinant enzyme for sodium phytate substrate of 0.105 ± 0.016 mM and 26.93 ± 1.21 mM min-1, respectively.展开更多
Stem bromelain is a plant thiol protease with several industrial and therapeutic applications. This current work presents kinetic studies of recombinant bromelain (recBM) expressed in Escherichia coli BL21-AI on fours...Stem bromelain is a plant thiol protease with several industrial and therapeutic applications. This current work presents kinetic studies of recombinant bromelain (recBM) expressed in Escherichia coli BL21-AI on foursynthetic substrates, N-α-carbobenzoxy-L-alanyl-p-nitrophenylester (ZANPE), N-α-carbobenzoxy-L-arginyl-L-ar-ginine-p-nitroanilide (ZAANA), N-α-carbobenzo-xy-L-phenylalanyl-L-valyl-L-arginine-p-nitroanili-de (ZPVANA) and L-pyroglutamyl-L-phenylalanyl-L-leucine-p-nitroanilide (PFLNA). Hydrolytic activities of recBM at various pH and temperature conditions were compared to that of commercial bromelain (cBM). Both enzymes demonstrated high activities at 45o C and pH 5 - 8 for recBM and pH 6 - 8 for cBM. recBM showed marginally lower Kmand slightly higher kcat/Kmfor ZAANA, ZANPE and ZPVANA in comparison to cBM.trans Epoxysuccinyl-L-leucylamido {4- guanidino}butane (E-64) severely affected recBM and cBM hydrolysis of the synthetic substrates by competitive inhibition with Kivalues of 3.6 - 5.1 μM and 5.5 - 6.9 μM for recBM and cBM, respectively. The evaluated properties of recBM including temperature and pH optima, substrate specificity and sensitivity to inhibitors or activators, satisfy the requisites required for food industries.展开更多
文摘Phytase, also known as phytate-degrading enzyme, catalyzes the hydrolysis of phytate (inositol hexakisphosphate) with sequential release of phosphate and lower inositol phosphate. We report here a new plasmid construct designated as pMSuia from pBAD-TOPO that harbors a 1.1 kb phytase gene (phyMS) from Mycobacterium smegmatis, and expression as well as characterization of the purified recombinant M. smegmatis phytase. DNA sequencing analysis and multiple alignment exercise indicated that the M. smegmatis phytase is different from both known acid and alkaline phytases. The active ~45 kDa recombinant enzyme was expressed and confirmed by enzyme assay and Western blot analyses. Ni-NTA affinity purified recombinant M. smegmatis phytase exhibited specific activity of 233.51 U/mg, optimal pH of 3 and 7 and optimal temperature of 60°C. The purified enzyme retains almost 30% of the initial activity after incubation at 90°C for 60 min. The enzyme showed broad substrate specificity with Km and Vmax of the recombinant enzyme for sodium phytate substrate of 0.105 ± 0.016 mM and 26.93 ± 1.21 mM min-1, respectively.
文摘Stem bromelain is a plant thiol protease with several industrial and therapeutic applications. This current work presents kinetic studies of recombinant bromelain (recBM) expressed in Escherichia coli BL21-AI on foursynthetic substrates, N-α-carbobenzoxy-L-alanyl-p-nitrophenylester (ZANPE), N-α-carbobenzoxy-L-arginyl-L-ar-ginine-p-nitroanilide (ZAANA), N-α-carbobenzo-xy-L-phenylalanyl-L-valyl-L-arginine-p-nitroanili-de (ZPVANA) and L-pyroglutamyl-L-phenylalanyl-L-leucine-p-nitroanilide (PFLNA). Hydrolytic activities of recBM at various pH and temperature conditions were compared to that of commercial bromelain (cBM). Both enzymes demonstrated high activities at 45o C and pH 5 - 8 for recBM and pH 6 - 8 for cBM. recBM showed marginally lower Kmand slightly higher kcat/Kmfor ZAANA, ZANPE and ZPVANA in comparison to cBM.trans Epoxysuccinyl-L-leucylamido {4- guanidino}butane (E-64) severely affected recBM and cBM hydrolysis of the synthetic substrates by competitive inhibition with Kivalues of 3.6 - 5.1 μM and 5.5 - 6.9 μM for recBM and cBM, respectively. The evaluated properties of recBM including temperature and pH optima, substrate specificity and sensitivity to inhibitors or activators, satisfy the requisites required for food industries.
