Structural highlights
Function
HIS6_THEMA IGPS catalyzes the conversion of PRFAR and glutamine to IGP, AICAR and glutamate. The HisF subunit catalyzes the cyclization activity that produces IGP and AICAR from PRFAR using the ammonia provided by the HisH subunit.[HAMAP-Rule:MF_01013]
Publication Abstract from PubMed
Nitrogen is incorporated into various metabolites by multifunctional glutamine amidotransferases via reactive ammonia generated by glutaminase hydrolysis of glutamine. Although this process is generally tightly regulated by subsequent synthase activity, little is known about how the glutaminase is inhibited in the absence of an activating signal. Here, we use imidazoleglycerolphosphate synthase as a model to investigate the mechanism of glutaminase regulation. A structure of the bienzyme-glutamine complex reveals that the glutaminase active site is in a catalysis-competent conformation but the ammonia pathway toward the synthase active site is blocked. Mutation of two residues blocking the pathway leads to a complete uncoupling of the two reactions and to a 2800-fold amplification of glutaminase activity. Our data advance the understanding of coupling enzymatic activities in glutamine amidotransferases and raise hypotheses of the underlying molecular mechanism.
Catalysis uncoupling in a glutamine amidotransferase bienzyme by unblocking the glutaminase active site.,List F, Vega MC, Razeto A, Hager MC, Sterner R, Wilmanns M Chem Biol. 2012 Dec 21;19(12):1589-99. doi: 10.1016/j.chembiol.2012.10.012. PMID:23261602[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ List F, Vega MC, Razeto A, Hager MC, Sterner R, Wilmanns M. Catalysis uncoupling in a glutamine amidotransferase bienzyme by unblocking the glutaminase active site. Chem Biol. 2012 Dec 21;19(12):1589-99. doi: 10.1016/j.chembiol.2012.10.012. PMID:23261602 doi:http://dx.doi.org/10.1016/j.chembiol.2012.10.012
