Funke Franziska Jasmin, Schlee Sandra, Bento Isabel, Bourenkov Gleb, Sterner Reinhard, Wilmanns Matthias
Institute of Biophysics and Physical Biochemistry, Regensburg Center for Biochemistry, University of Regensburg, Regensburg 93040, Germany.
European Molecular Biology Laboratory, Hamburg Unit, Hamburg 22607, Germany.
ACS Catal. 2025 Mar 7;15(5):4359-4373. doi: 10.1021/acscatal.4c07438. Epub 2025 Feb 26.
Glutamine amidotransferases are multienzyme machineries in which reactive ammonia is generated by a glutaminase and then transferred through a sequestered protein tunnel to a synthase active site for incorporation into diverse metabolites. To avoid wasteful metabolite consumption, there is a requirement for synchronized catalysis, but any generally applicable mechanistic insight is still lacking. As synthase activity depends on glutamine turnover, we investigated possible mechanisms controlling glutaminase catalysis using aminodeoxychorismate synthase involved in folate biosynthesis as a model. By analyzing this system in distinct states of catalysis, we found that incubation with glutamine leads to a subunit interface expansion by one-third of its original area. These changes completely enclose the glutaminase active site for sequestered catalysis and the subsequent transport of volatile ammonia to the synthase active site. In view of similar rearrangements in other glutamine amidotransferases, our observations may provide a general mechanism for the catalysis synchronization of this multienzyme family.
谷氨酰胺氨基转移酶是多酶体系，其中谷氨酰胺酶产生活性氨，然后通过一个封闭的蛋白质通道将其转移到合成酶活性位点，以掺入各种代谢产物中。为避免代谢产物的浪费消耗，需要同步催化，但仍缺乏普遍适用的机制见解。由于合成酶活性取决于谷氨酰胺的周转，我们以参与叶酸生物合成的氨基脱氧分支酸合成酶为模型，研究了控制谷氨酰胺酶催化的可能机制。通过分析该系统在不同催化状态下的情况，我们发现与谷氨酰胺孵育会导致亚基界面扩大，扩大幅度为其原始面积的三分之一。这些变化完全封闭了谷氨酰胺酶活性位点，以进行隔离催化，并随后将挥发性氨转运到合成酶活性位点。鉴于其他谷氨酰胺氨基转移酶中存在类似的重排，我们的观察结果可能为这个多酶家族的催化同步提供一种普遍机制。
