[4] Aldehyde oxidoreductases and other molybdenum-containing enzymes

Publisher Summary This chapter describes aldehyde oxidoreductases and other molybdenum (Mo)-containing enzymes. Desulfovibrio gigas ( D. gigas ) Mo -containing protein is isolated on the basis of its optical absorption characteristics.Mo was first detected by electron paramagnetic resonance (EPR). All purification operations for aldehyde oxidoreductases are carried out at 4, starting from a D. gigas NCIB 9332 cell-free crude extract. Activity is determined aerobically at 25 by measuring the rate of 2, 6-dichlorophenol-indophenol (DCPIP) reduction at 600 nm ) in a 1-cm optical path spectrophotometer quartz cell. A pH profile of the enzyme activity is determined in different buffer systems, such as citrate, phosphate, Tris-HCl, and Tris-glycine—covering a pH range of 4–11. DCPIP and ferricyanide are shown to be capable of cycling the electronic flow, whereas other cation and anion dyes do not. The visible absorption spectrum of the protein is similar to that observed for the deflavo forms of xanthine and aldehyde oxidases and reminiscent of the one observed for plant-type ferredoxins.