GLUTATHIONE-S-TRANSFERASE ACTIVITY IN SPRUCE NEEDLES

Glutathione S-transferase activity was present in extracts from needles of two different spruce species (Picea abies and Picea glauca). In vitro conjugation studies were conducted with three 14C herbicides and one 14C fungicide: atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), fluorodifen (2,4′-dinitro-4-trifluoromethyl diphenyl-ether), propachlor (2-chloro-N-isopropylacetanilide), and pentachloronitrobenzene (PCNB). The enzymes from both P. abies and P. glauca showed the highest rates of enzymatic conjugation for fluorodifen as the substrate while intermediate to low rates of enzymatic conjugation were observed with PCNB and propachlor. Atrazine was not an appreciable substrate for the enzymes of either species. The water-soluble 14C conjugation products of the enzymatic reactions were assayed by liquid scintillation spectrometry. The [14C]glutathione conjugates from fluorodifen and PCNB were identified by a combination of thinlayer chromatography (TLC), high-performance liquid chromatography (HPLC), and fast atom bombardment mass spectrometry and the [14C]glutathione conjugate of propachlor was identified by TLC and HPLC comparison to an authentic standard. The catalytic properties of glutathione S-transferase from P. abies were analyzed with CDNB as substrate. The apparent KM values were 0.14 mM for GSH and 0.67 mM for CDNB, respectively, the pH optimum was between 7.6 and 8.0, and the temperature optimum was 40-45°C. The activation energy was calculated to be 32.4 kJ mol-1. © 1990.