PT  - JOURNAL ARTICLE
AU  - Vijay Jayaraman
AU  - D. John Lee
AU  - Nadav Elad
AU  - Shay Vimer
AU  - Michal Sharon
AU  - James S. Fraser
AU  - Dan S. Tawfik
TI  - <em>A counter-enzyme complex regulates</em> glutamate metabolism in <em>Bacillus subtilis</em>
AID  - 10.1101/2021.04.12.439528
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.04.12.439528
4099  - http://biorxiv.org/content/early/2021/04/12/2021.04.12.439528.short
4100  - http://biorxiv.org/content/early/2021/04/12/2021.04.12.439528.full
AB  - Multi-enzyme assemblies composed of metabolic enzymes catalyzing sequential reactions are being increasingly studied. Here, we report the discovery of a 1.6 megadalton multi-enzyme complex from Bacillus subtilis composed of two enzymes catalyzing opposite rather than sequential reactions (“counter-enzymes”): glutamate synthase (GltAB), and glutamate dehydrogenase (GudB), that make and break glutamate, respectively. In vivo and in vitro studies show that the primary role of complex formation is to inhibit GudB’s activity as this enzyme is constitutively expressed including in glutamate-limiting conditions. Using cryo-electron microscopy, we elucidated the structure of the complex and the basis of GudB’s inhibition. Finally, we show that this complex that exhibits unusual oscillatory progress curves is a necessity for planktonic growth in glutamate-limiting conditions, but is also essential for biofilm growth in glutamate-rich media, suggesting a regulatory role at fluctuating glutamate concentrations.Competing Interest StatementThe authors have declared no competing interest.