Mayoral Jaime G, Nouzova Marcela, Yoshiyama Michiyo, Shinoda Tetsuro, Hernandez-Martinez Salvador, Dolghih Elena, Turjanski Adrian G, Roitberg Adrian E, Priestap Horacio, Perez Mario, Mackenzie Lucy, Li Yiping, Noriega Fernando G
Department of Biological Sciences, Florida International University, 11200 SW 8th Street, Miami, FL 33199, USA.
Insect Biochem Mol Biol. 2009 Jan;39(1):31-7. doi: 10.1016/j.ibmb.2008.09.010. Epub 2008 Oct 17.
A juvenile hormone acid methyltransferase (JHAMT) was isolated as an abundant EST in a library of the corpora allata of the adult female mosquito Aedes aegypti. Its full length cDNA encodes a 278-aa protein that has 43% amino acid identity with BmJHAMT, a juvenile hormone acid methyltransferase previously cloned from Bombyx mori. Heterologous expression produced a recombinant protein that metabolizes farnesoic acid (FA) into methyl farnesoate, as well as juvenile hormone acid into juvenile hormone III (JH III) with exquisite stereo specificity. Real time PCR experiments showed that JHAMT mRNA levels are not an unequivocal indicator of JH III synthesis rates; the A. aegypti JHAMT gene, silent in female pupae, was transcriptionally activated just 4-6h before adult eclosion. Radiochemical methyltransferase assays using active and inactive corpora allata glands (CA) dissected from sugar and blood-fed females respectively, clearly indicated that significant levels of JHAMT enzymatic activity are present when the CA shows very low spontaneous rates of JH III synthesis. Having the last enzymes of the JH synthetic pathway readily available all the time might be critical for the adult female mosquito to sustain rapid dynamic changes in JH III synthesis in response to nutritional changes or peripheral influences, such as mating or feeding. These results suggest that this gene has different roles in the regulation of JH synthesis in pupal and adult female mosquitoes, and support the hypothesis that the rate-limiting steps in JH III synthesis in adult female mosquitoes are located before entrance of FA into the synthetic pathway.
一种保幼激素酸甲基转移酶（JHAMT）作为丰富的EST，在成年雌性埃及伊蚊咽侧体文库中被分离出来。其全长cDNA编码一个278个氨基酸的蛋白质，该蛋白质与先前从家蚕中克隆的保幼激素酸甲基转移酶BmJHAMT具有43%的氨基酸同一性。异源表达产生了一种重组蛋白，该蛋白能将法尼酸（FA）代谢为法尼酸甲酯，同时将保幼激素酸代谢为保幼激素III（JH III），具有极高的立体特异性。实时PCR实验表明，JHAMT mRNA水平并非JH III合成速率的明确指标；埃及伊蚊JHAMT基因在雌性蛹期沉默，在成虫羽化前4 - 6小时才被转录激活。分别使用从取食糖水和血液的雌性蚊子中解剖得到的活性和非活性咽侧体腺（CA）进行放射化学甲基转移酶测定，结果清楚地表明，当CA显示出极低的JH III自发合成速率时，仍存在显著水平的JHAMT酶活性。始终具备保幼激素合成途径的最后一种酶，对于成年雌性蚊子维持保幼激素III合成的快速动态变化以应对营养变化或外周影响（如交配或进食）可能至关重要。这些结果表明，该基因在蛹期和成年雌性蚊子保幼激素合成的调控中具有不同作用，并支持这样一种假说，即成年雌性蚊子保幼激素III合成中的限速步骤位于法尼酸进入合成途径之前。
