+ Resolve Article
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter

+ Translate
+ Subscribe to Site Feed
GeoScience Most Shared ContentMost Shared Content

Quantifying the allosteric properties of Escherichia coli carbamyl phosphate synthetase: determination of thermodynamic linked-function parameters in an ordered kinetic mechanism

, : Quantifying the allosteric properties of Escherichia coli carbamyl phosphate synthetase: determination of thermodynamic linked-function parameters in an ordered kinetic mechanism. Biochemistry 31(8): 2309-2316

The effects of the allosteric ligands UMP, IMP, and ornithine on the partial reactions catalyzed by Escherichia coli carbamyl phosphate synthetase have been examined. Both of these reactions, a HCO3(-)-dependent ATP synthesis reaction and a carbamyl phosphate-dependent ATP synthesis reaction, follow bimolecular ordered sequential kinetic mechanisms. In the ATPase reaction, MgATP binds before HCO3- as established previously for the overall reaction catalyzed by carbamyl phosphate synthetase [Raushel, F. M., Anderson, P. M., & Villafranca, J. J. (1978) Biochemistry 17, 5587-5591]. The initial velocity kinetics for the ATP synthesis reaction indicate that MgADP binds before carbamyl phosphate in an equilibrium ordered mechanism except in the presence of ornithine. Determination of true thermodynamic linked-function parameters describing the impact of allosteric ligands on the binding interactions of the first substrate to bind in an ordered mechanism requires experiments to be performed in which both substrates are varied even if only one is apparently affected by the allosteric ligands. In so doing, we have found that IMP has little effect on the overall reaction of either of these two partial reactions. UMP and ornithine, which have a pronounced effect on the apparent Km for MgATP in the overall reaction, both substantially change the thermodynamic dissociation constant for MgADP from the binary E-MgADP complex, Kia, in the ATP synthesis reaction, with UMP increasing Kia 15-fold and ornithine decreasing Kia by 18-fold. By contrast, only UMP substantially affects the Kia for MgATP in the ATPase reaction, increasing it by 5-fold.


PMID: 1531767

Other references

Campbell, T., 2005: The cognitive neuroscience of auditory distraction. We are often aware of the content of distracting sound, although typically remain unaware of the processes by which that sound is disruptive. Disruption can occur even when the sound is ignored and unrelated to the task being performed. In a recen...

Cowgill W.P.Jr; Maletta M.H.; Johnston S.A., 1992: Evaluation of two disease forecasting systems for controlling early blight on tomato in new jersey. Hortscience 27(6): 629

Beckmeyer, D., 1987: Review from Harborview Medical Center, Seattle. Journal of Burn Care & Rehabilitation 8(4): 339-340

Norton, L., 1994: Salvage chemotherapy of breast cancer. Stage IV breast cancer (metastatic foci beyond the axillary lymph nodes) initially may respond well to systemic salvage therapy with hormonal or chemotherapy drugs. Hormonal therapy is preferred because of its lower toxicity. Patients who eventual...

Phu, J.; Khuu, S.K.; Yapp, M.; Assaad, N.; Hennessy, M.P.; Kalloniatis, M., 2017: The value of visual field testing in the era of advanced imaging: clinical and psychophysical perspectives. White-on-white standard automated perimetry (SAP) is widely used in clinical and research settings for assessment of contrast sensitivity using incremental light stimuli across the visual field. It is one of the main functional measures of the eff...

Das, K.P.; Datta, N.K.; Chowdhury, R.M.; Alam, M.S.; Kaiser, M.S., 2014: Outcome of early active mobilization in flexor tendon repair in zone II in hand. Early controlled motion programs after flexor tendon repair in zone II of hand are designed to minimize adhesion formation by promoting the excursion of repaired tendons. The flexor tendon surgery especially in zone II is complicated. It is simple...

Anonymous, 2006: Use of chlorofluorocarbons in hydrology: a guidebook. This guidebook aims to facilitate a comparative analysis of chlorofluorocarbon (CFC) and isotope techniques for quantifying groundwater recharge and a wider use of the CFC technique under appropriate conditions by providing a description of its sc...

Ribes, J.; Ribes, E., 2002: Miridae from Andorra not recorded in the Catalogue of Palaerctic Heteroptera Miridos del Principado de Andorra no citados en el Catalogue of Palaearctic Heteroptera. Some data on the Heteroptera fauna of Andorra are presented. Three taxa are recorded as new to the Iberian fauna, Lygocoris rugicollis (Fallen), Strongylocoris niger (Herrich-Schaffer) and Atractotomus marcoi.

Lister, J., 1968: Modern man. New England Journal of Medicine 279(18): 985-987

Druilhe, P.; Pérignon, J.L., 1996: Which vaccine against malaria?. Archives de Pediatrie 3 Suppl 1: 334s-335s