Effect of the Synthetic Putrescine Analogue (E)-1,4-Diaminobut-2-ene on Uptake of Methionine, Polymines, and Sugars inPyrenophora avenae

Methionine uptake by the oat stripe pathogenPyrenophora avenaewas significantly reduced following exposure to the synthetic putrescine analogue (E)-1,4-diaminobut-2-ene (E-BED) for 2 days. Exposure of the fungus to E-BED for just 4 hr also resulted in decreased methionine uptake, although the effect was not as marked. Similar effects on methionine uptake were observed whenP. avenaewas grown in medium amended with 1 mMof the E-BED derivative (E)-N,N,N′,N′-tetraethyl-1,4-diaminobut-2-ene. Exposure to E-BED for 2 days or 4 hr also resulted in significant reductions in uptake of the amino acid ornithine and the polyamines putrescine, spermidine, and spermine and the sugars fructose and glucose. Growth ofP. avenaein E-BED had no effect on theKmfor methionine or fructose uptake, but reducedVmaxconsiderably in both cases. The data suggest that E-BED is a noncompetitive inhibitor of methionine and fructose uptake inP. avenae.Decreased methionine uptake and subsequent intracellular depletion may be responsible for the E-BED-induced reduction inS-adenosylmethionine decarboxylase (AdoMetDC) activity, since addition of methionine to E-BED-treated tissue restored AdoMetDC activity.