Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Nitroreductase II Involved in 2,4,6-Trinitrotoluene Degradation: Purification and Characterization from Klebsiella sp. C1: Jung-Hye Shin , Hong-Gyu Song; J. Microbiol. 2009;47(5):536-541. Published online October 24, 2009; DOI: https://doi.org/10.1007/s12275-008-0171-6

Abstract: Three 2,4,6-trinitrotoluene (TNT) nitroreductases from Klebsiella sp. C1 have different reduction capabilities that can degrade TNT by simultaneous utilization of two initial reduction pathways. Of these, nitroreductase II was purified to homogeneity by sequential chromatographies. Nitroreductase II is an oxygen- insensitive enzyme and reduces both TNT and nitroblue tetrazolium. The N-terminal amino acid sequence of the enzyme did not show any sequence similarity with those of other nitroreductases reported. However, it transformed TNT by the reduction of nitro groups like nitroreductase I. It had a higher substrate affinity and specific activity for TNT reduction than other nitroreductases, and it showed a higher oxidation rate of NADPH with the ortho-substituted isomers of TNT metabolites (2-hydroxylaminodinitrotoluene and 2-aminodinitrotoluene) than with para-substituted compounds (4-hydroxylaminodinitrotoluene and 4-aminodinitrotoluene).

Purification and Characterization of an Intracellular NADH: Quinone Reductase from Trametes versicolor: Sang-Soo Lee , Dong-Soo Moon , Hyoung T. Choi , Hong-Gyu Song; J. Microbiol. 2007;45(4):333-338.; DOI: https://doi.org/2564 [pii]

Abstract: Intracellular NADH:quinone reductase involved in degradation of aromatic compounds including lignin was purified and characterized from white rot fungus Trametes versicolor. The activity of quinone reductase was maximal after 3 days of incubation in fungal culture, and the enzyme was purified to homogeneity using ion-exchange, hydrophobic interaction, and gel filtration chromatographies. The purified enzyme has a molecular mass of 41 kDa as determined by SDS-PAGE, and exhibits a broad temperature optimum between 20-40°C, with a pH optimum of 6.0. The enzyme preferred FAD as a cofactor and NADH rather than NADPH as an electron donor. Among quinone compounds tested as substrate, menadione showed the highest enzyme activity followed by 1,4-benzoquinone. The enzyme activity was inhibited by CuSO4, HgCl2, MgSO4, MnSO4, AgNO3, dicumarol, KCN, NaN3, and EDTA. Its Km and Vmax with NADH as an electron donor were 23 μM and 101 mM/mg per min, respectively, and showed a high substrate affinity. Purified quinone reductase could reduce 1,4-benzoquinone to hydroquinone, and induction of this enzyme was higher by 1,4-benzoquinone than those of other quinone compounds.

Purification and Characterization of Laccase from the White Rot Fungus Trametes versicolor: Moon-Jeong Han , Hyoung-Tae Choi , Hong-Gyu Song; J. Microbiol. 2005;43(6):555-560.; DOI: https://doi.org/2290 [pii]

Abstract: Laccase is one of the ligninolytic enzymes of white rot fungus Trametes versicolor 951022, a strain first isolated in Korea. This laccase was purified 209-fold from culture fluid with a yield of 6.2% using ethanol precipitation, DEAE-Sepharose, Phenyl-Sepharose, and Sephadex G-100 chromatography. T. versicolor 951022 excretes a single monomeric laccase showing a high specific activity of 91,443 U/mg for 2,2''-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) as a substrate. The enzyme has a molecular mass of approximately 97 kDa as determined by SDS-PAGE, which is larger than those of other laccases reported. It exhibits high enzyme activity over broad pH and temperature ranges with optimum activity at pH 3.0 and a temperature of 50oC. The Km value of the enzyme for substrate ABTS is 12.8 M and its corresponding Vmax value is 8125.4 U/mg. The specific activity and substrate affinity of this laccase are higher than those of other white rot fungi, therefore, it may be potentially useful for industrial purposes.

Purification and characterization of a xylanase from alkalophilic cephalosporium sp. RYM-202: Kang, Myoung Kyu , Kwon, Tae Ik , Yang, Young Ki , Rhee, Young Ha; J. Microbiol. 1995;33(2):109-114.

Abstract: Alkalophilic Cephalosporium sp. RYM-202 produced multiple xylanases extracellularly. One of these xylanases was purified to electrophoretical homogeneity by chromatography with DEAE-Sephadex A-50, Sephacryl S-200 HR and Superose 12 HR. The purified xylanase differed from most other microbial xylanases in that it had low-molecular weight and acidic isoelectric point. The molecular weight of the xylanase in that it had low-molecular weight and acidic isoelectric point. The molecular weight of the xylanase was 23 kDa by SDS-polyacrylamide electrophoresis and 24 kDa by gel permeation chromatography, and the isoelectric point was 4.3. The xylanase had the highest activity permentation chromatography, and the isoelectric point was 4.3. The xylanase had the highest activity permeation chromatography, and the isoelectric point was 4.3. The xylanase had the highest activity at pH 8.0 and 50℃. It was stable over a wide range of pH and retained more than 80% of its original activity after 24 h of incubation even at pH 12. The Km values of this enzyme on birchwood xylan and oat spelts xylan were 2.33 and 3.45 mg/ml, respectively. The complete inhibition of the enzyme of n-bromosuccinimide suggests the involvement of tryptophan in the active site. The sylanase lacked activity towards crystalline cellulose and carboxymethyl cellulose.

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