Purification and Some Properties of Two Principal Enzymes of the Thiosulphate - oxidizing Multi - enzyme System from ThiobaciZZus A 2 By WEI - PING

A soluble thiosulphate-oxidizing multi-enzyme system, precipitated from a crude cell extract of Thiobacillus A2 with ammonium sulphate, has been resolved into four essential components by DEAE-Sepharose chromatography, gel filtration of Sephadex G-1 00 and G-200, hydrophobic interaction chromatography on phenyl-Sepharose and preparative isoelectric focusing. Oxidation of thiosulphate to sulphate coupled to the reduction of horse-heart cytochrome c as electron acceptor was catalysed by two colourless proteins (enzyme A: M,, 16000; and enzyme B : M, ,64 000), cytochrome c5 5 2.5 (M, , 32 OOO) and ‘cytochrome c5 ’ (M,, 300 000). Enzymes A and B were purified 110and 280-fold, respectively. Sulphite : cytochrome c oxidoreductase was also purified 660-fold. The mechanism of action of the system is discussed.