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( Angelica Moreno Enriquez ),( Zahaed Evangelista Martinez ),( Luis Servin Gonzalez ),( Maria Elena Flores Carrasco ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.8
The aim of the present work was to examine the putative promoter region of the operon ansPAB and to determine the general elements required for the regulation of transcriptional activity. The transcriptional start site of the ansPAB promoter was determined by using highresolution S1-nuclease mapping. Sequence analysis of this region showed -10 and -35 elements, which were consistent with consensus sequences for R. etli promoters that are recognized by the major form of RNA polymerase containing the σ70 transcription factor. Mutation studies affecting several regions located upstream of the transcriptional start site confirmed the importance of these elements on transcriptional expression.
( Moreno Enriquez Angelica ),( Zahaed Evangelista Martinez ),( Edith G. Gonzalez-mondragon ),( Arturo Calderon Flores ),( Roberto Arreguin ),( Ernesto Perez Rueda ),( Alejandro Huerta Saquero ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.3
We report the expression, purification, and characterization of L-asparaginase (AnsA) from Rhizobium etli. The enzyme was purified to homogeneity in a single-step procedure involving affinity chromatography, and the kinetic parameters Km, Vmax, and kcat for L-asparagine were determined. The enzymatic activity in the presence of a number of substrates and metal ions was investigated. The molecular mass of the enzyme was 47 kDa by SDS-PAGE. The enzyme showed a maximal activity at 50oC, but the optimal temperature of activity was 37oC. It also showed maximal and optimal activities at pH 9.0. The values of Km, Vmax, kcat, and kcat/Km were 8.9±0.967×10-3 M, 128±2.8 U/mg protein, 106±2 s-1, and 1.2±0.105×104M-1s-1, respectively. The L-asparaginase activity was reduced in the presence of Mn2+, Zn2+, Ca2+, and Mg2+ metal ions for about 52% to 31%. In addition, we found that NH4 +, L-Asp, D-Asn, and β-aspartyl-hydroxamate in the reaction buffer reduced the activity of the enzyme, whereas L-Gln did not modify its enzymatic activity. This is the first report on the expression and characterization of the L-asparaginase (AnsA) from R. etli. Phylogenetic analysis of asparaginases reveals an increasing group of known sequences of the Rhizobialtype asparaginase II family.