An enzyme possessing both glutathione-dependent formaldehyde dehydrogenase and S-nitrosoglutathione reductase from Antrodia camphorata

Glutathione-dependent formaldehyde dehydrogenase (GFD or GSH-FDH) plays important roles in formaldehyde detoxification and antioxidation. A gene encoding GFD from Antrodia camphorata was identified based on sequence homology. The deduced amino acid sequence of 378 amino acid residues is conserved among the reported GFDs. To characterise the Ac-GFD, the coding region was subcloned into a vector pET-20b(+) and transformed into Escherichia coli. The recombinant GFD was expressed and purified by Ni2+-nitrilotriacetic acid Sepharose. This purified enzyme showed a single band on a 10% SDS–PAGE. The enzyme retained 50% GFD activity after heating at 50 °C for 5 min. The enzyme is bifunctional. In addition to the GFD activity, it also functions as an effective S-nitrosoglutathione reductase (GSNOR) presumably to safeguard against nitrosative stress. The Km values for S-hydroxymethylglutathione and S-nitrosoglutathione were 1.20 and 0.28 mM, respectively.