The purification and properties of glutathione S-transferase from Ditylenchus myceliophagus

The cytoplasmic glutathione S-transferase (GST) activity of Ditylenchus myceliophagus was resolved into four isoforms, DmI, DmII, DmIII and DmIV, by a combination of chromatofocusing and hexylglutathione affinity chromatography. An endogenous cytoplasmic factor interfered with the binding of the cytosolic transferases to glutathione and hexylglutathione affinity matrices and binding only occurred after initial purification. The four isoforms were homodimers with subunit molecular weights 25.3, 24, 26 and 25.7 kDa for DmI, II, III and IV, respectively. The pIs for DmI, II and III were 7.28, 5.04 and 4.88. The N-terminal sequence of the major form (DmIII) had a strong sequence similarity to the mammalian alpha class GSTs. However, substrate specificities and inhibitor profiles of Dm II, III and IV showed an overall resemblance to the mammalian mu class, whilst DmI showed more alpha class characteristics.