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Tsutomu Shimizu, Naoya Hashimoto, Ishizue Nakayama, Tohru Nakao, Hiroyuki Mizutani, Tadaaki Unai, Mikio Yamaguchi, Hiroshi Abe, A Novel Isourazole Herbicide, Fluthiacet-Methyl, is a Potent Inhibitor of Protoporphyrinogen Oxidase after Isomerization by Glutathione S-Transferase, Plant and Cell Physiology, Volume 36, Issue 4, June 1995, Pages 625–632, https://doi.org/10.1093/oxfordjournals.pcp.a078802
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Abstract
A novel isourazole herbicide, fluthiacet-methyl (methyl [[2-chloro-4-fluoro-5-[(5,6,7,8-tetrahydro- 3-oxo-lH,3H-[l,3,4]thiadiazolo[3,4-a]pyridazin-l-ylidene)amino]phenyrjthio]acetate; experimental code name, KIH-9201) promoted the leakage of electrolytes from cotyledons of velvetleaf (Abtilon theophtasti Medic) and cotton (Gossypium hirsutum L.) plants that are sensitive to this compound. It induced the accumulation of protoporphyrin IX in cotyledons of cotton and inhibited Chl biosynthesis in cotyledons of velvetleaf and cotton at low concentrations (I50 values, 10–12 nM). Fluthiacet-methyl was converted to its urazole by glutathione S-transferase that had been partially purified from velvetleaf. The urazole inhibited protoporphyrinogen oxidase (Protox, EC 1.3.3.4) from some plants, including velvetleaf, at low concentrations (I50 values, 5.1–11 nM), whereas fluthiacet-methyl was not as potent. The effects in vivo (electrolyte leakage and inhibition of Chi biosynthesis) of fluthiacet-methyl were correlated with the inhibition of Protox activity by the urazole and not with the action of fluthiacet-methyl itself. From these results, it is concluded that fluthiacet-methyl inhibits Protox activity after conversion to the corresponding urazole by glutathione S-transferase. It is in this way that fluthiacet-methyl exerts its effect as a light-dependent peroxidizing herbicide.
