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10-formyltetrahydrofolate synthetase activity in normal and Brugia pahangi-infected Aedes aegypti
Ist Teil von
The Journal of parasitology, 1979-04, Vol.65 (2), p.226-232
Ort / Verlag
United States: American Society of Parasitologists
Erscheinungsjahr
1979
Link zum Volltext
Quelle
Free E-Journal (出版社公開部分のみ）
Beschreibungen/Notizen
The activity of 10-formyltetrahydrofolate synthetase (f10FH4S) in crude extracts of 4- to 5-day-old adult male and uninfected female Aedes aegypti was higher than that of other folate-related enzymes studied so far. L-Cysteine, Mg2+, and NH4+ were required for optimal activity of this enzyme in the forward direction (forming f10FH4, ADP and Pi). The apparent Km values of the substrates and cofactors for the forward reaction showed correspondence between ATP and Mg2+ (both 0.07 mM) and formate and NH4+ (13 mM and 7 mM); the apparent Km value of FH4 (0.26 mM) corresponded closely to the Ki value of the 4-amino analog of folate methotrexate (0.24 mM), the latter being a competitive inhibitor of the enzyme. The estimated molecular weight of A. aegypti f10FH4S was 260,000. Two compounds were relatively strong inhibitors of the enzyme, as indicated by their ID50 value: methotrexate (2 μ M) and suramin (8 μ M). The activity of f10FH4S was approximately 40% lower in uninfected female mosquitoes more than a week old than in those only 5 days old. The activity of this enzyme in female mosquitoes 7 days after they fed upon Brugia pahangi-iniected jirds was approximately the same as that in age-matched uninfected females. However, the activity of f10FH4S in female mosquitoes 12 days after infection with B. pahangi was 50% lower than that in age-matched uninfected females. The significance of this latter finding is discussed.