ABSTRACT

Glutamine: fructose-6-phosphate amidotransferase (GFAT) enzymes catalyse the first committed step of the hexosamine biosynthesis pathway (HBP) using glutamine and fructose-6-phosphate to form glucosamine-6-phosphate (GlcN6P). Numerous species (e.g. mouse, rat, zebrafish, chicken) including humans and Drosophila encode two broadly expressed copies of this enzyme but whether these perform redundant, partially overlapping or distinct functions is not known. To address this question, we produced single gene null mutations in the fly counterparts of gfat1 and gfat2. Deletions for either enzyme were fully lethal and homozygotes lacking either GFAT1 or GFAT2 died at or prior to the first instar larval stage. Therefore, when genetically eliminated, neither isoform was able to compensate for the other. Importantly, dietary supplementation with D-glucosamine-6-phosphate rescued GFAT2 deficiency and restored viability to gfat2^−/- mutants. In contrast, glucosamine-6-phosphate did not rescue gfat1^−/- animals.

摘要

谷氨酰胺：6-磷酸果糖氨基转移酶 (GFAT) 酶催化己糖胺生物合成途径 (HBP) 的第一步，使用谷氨酰胺和 6-磷酸果糖形成 6-磷酸葡萄糖胺 (GlcN6P)。包括人类和果蝇在内的许多物种（例如小鼠、大鼠、斑马鱼、鸡）编码这种酶的两个广泛表达的拷贝，但它们是否执行冗余、部分重叠或不同的功能尚不清楚。为了解决这个问题，我们在gfat1和gfat2的苍蝇对应物中产生了单基因无效突变. 任何一种酶的缺失都是完全致命的，缺乏 GFAT1 或 GFAT2 的纯合子在第一龄幼虫阶段或之前死亡。因此，当基因消除时，两种异构体都无法补偿另一种。重要的是，膳食补充 D-氨基葡萄糖 6-磷酸盐可挽救 GFAT2 缺陷并恢复gfat2 ^-/- 突变体的活力。相反，6-磷酸氨基葡萄糖没有拯救gfat1 ^-/- 动物。