Cloning and characterization of a thermostable glutathione reductase from a psychrophilic Arctic bacterium Sphingomonas sp

• Published in: FEMS Microbiology Letters
• Main Authors: VuThi, Hai, Jang, Sei-Heon, Lee, ChangWoo
• Other Authors: Daegu University Research Grant
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2019
• Subjects: Arctic
• Online Access: http://dx.doi.org/10.1093/femsle/fnz218; http://academic.oup.com/femsle/advance-article-pdf/doi/10.1093/femsle/fnz218/30194884/fnz218.pdf; https://academic.oup.com/femsle/article-pdf/366/18/fnz218/42816832/fnz218.pdf

ABSTRACT Glutathione reductase is an important oxidoreductase that helps maintain redox homeostasis by catalyzing the conversion of glutathione disulfide to glutathione using NADPH as a cofactor. In this study, we cloned and characterized a glutathione reductase (hereafter referred to as SpGR) from Sphingomonas sp. PAMC 26621, an Arctic bacterium. SpGR comprises 449 amino acids, and functions as a dimer. Surprisingly, SpGR exhibits characteristics of thermophilic enzymes, showing optimum activity at 60°C and thermal stability up to 70°C with ∼50% residual activity at 70°C for 2 h. The amino acid composition analysis of SpGR showed a 1.9-fold higher Arg content (6%) and a 2.7-fold lower Lys/Arg ratio (0.75) compared to the Arg content (3.15%) and the Lys/Arg ratio (2.01) of known psychrophilic glutathione reductases. SpGR also exhibits its activity at 4°C, and circular dichroism and fluorescence spectroscopy results indicate that SpGR maintains its secondary and tertiary structures within the temperature range of 4–70°C. Taken together, the results of this study indicate that despite its origin from a psychrophilic bacterium, SpGR has high thermal stability. Our study provides an insight into the role of glutathione reductase in maintaining the reducing power of an Arctic bacterium in a broad range of temperatures.