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- Isoforms of Glucose 6-Phosphate Dehydrogenase in Deinococcus radiophilus
- Ji Youn Sung , Young Nam Lee
- J. Microbiol. 2007;45(4):318-325.
- DOI: https://doi.org/2566 [pii]
- 216 View
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Abstract
PDF - Glucose 6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) in Deinococcus radiophilus, an extraordinarily UV-resistant bacterium, was investigated to gain insight into its resistance as it was shown to be involved in a scavenging system of superoxide (O2-1) and peroxide (O2-2) generated by UV and oxidative stresses. D. radiophilus possesses two G6PDH isoforms: G6PDH-1 and G6PDH-2, both showing dual coenzyme specificity for NAD and NADP. Both enzymes were detected throughout the growth phase; however, the substantial increase in G6PDH-1 observed at stationary phase or as the results of external oxidative stress indicates that this enzyme is inducible under stressful environmental conditions. The G6PDH-1 and G6PDH-2 were purified 122- and 44-fold (using NADP as cofactor), respectively. The purified G6PDH-1 and G6PDH-2 had the specific activity of 2,890 and 1,033 U/mg protein (using NADP as cofactor) and 3,078 and 1,076 U/mg protein (using NAD as cofactor), respectively. The isoforms also evidenced distinct structures; G6PDH-1 was a tetramer of 35 kDa subunits, whereas G6PDH-2 was a dimer of 60 kDa subunits. The pIs of G6PDH-1 and G6PDH-2 were 6.4 and 5.7, respectively. Both G6PDH-1 and G6PDH-2 were inhibited by both ATP and oleic acid, but G6PDH-1 was found to be more susceptible to oleic acid than G6PDH-2. The profound inhibition of both enzymes by β-naphthoquinone-4-sulfonic acid suggests the involvement of lysine at their active sites. Cu2+ was a potent inhibitor to G6PDH-2, but a lesser degree to G6PDH-1. Both G6PDH-1 and G6PDH-2 showed an optimum activity at pH 8.0 and 30°C.
- Occurrence of Thioredoxin Reductase in Deinococcus Species, the UV resistant Bacteria
- Hee Jeong Seo , Young Nam Lee
- J. Microbiol. 2006;44(4):461-465.
- DOI: https://doi.org/2404 [pii]
- 210 View
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Abstract
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- The occurrence of thioredoxin reductase (NAD(P)H: oxidized-thioredoxin reductase, EC 1.6.4.5, TrxR) in five mesophilic species of Deinococcus was investigated by PAGE. Each species possessed a unique TrxR pattern, for example, a single TrxR characterized D. radiopugnans while multiple forms of TrxR occurred in other Deinococcal spp. Most of TrxRs occurring in Deinococcus showed dual cofactor specificity, active with either NADH or NADPH, although the NADPH specific-TrxR was observed in D. radiophilus and D.proteolyticus.
- Purification and Characterization of Catalase-3 of Deinococcus radiophilus
- Lee, In Jeong , Lee, Young Nam
- J. Microbiol. 1995;33(3):239-243.
- 217 View
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Abstract
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- Deinococcus radiophilus, an UV resistant bacterium seemed to contain three issoenzymes of catalase. Among them, the samllest and most abundant species in cell-free extract, catalase-3 which also exhibited peroxidase activity was purified to electrophoretic homogeneity (145-fold purification) by chromatographic procedures. Its molecular weight was 155 kDa composed of four 38 kDa subunits. The K_m value of catalase-3 for H₂O₂was approximately 0.5 mM. This enzyme showed a typical ferric heme spectrum with maximum absorption at 405 nm. Upon binding to cyanide, the 405 nm peak shifted to 420 nm. Catalase-3 was very sensitive to inhibitors of heme proteins, such as cyanide, azide and hydroxylamine. A ratio of A_405/A_28O was 0.5 Catalase-3 was active over a wide range of pH, between pH 7 and 10. The enzyme was rather heat-labile and partially sensitive to ethanol-chloroform treatment, but resistant to 3-amino-1, 2, 4-triazole. Catalase-3 of D. radiophilus, which is a bifunction catalatic peroxidatic enzyme seemed to share certain molecular properties with the typical catalase and the catalase-peroxidase along with its own unique features.
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