geoscience.net logo
+ 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

Reactivity of the essential thiol of Klebsiella aerogenes urease. Effect of pH and ligands on thiol modification


, : Reactivity of the essential thiol of Klebsiella aerogenes urease. Effect of pH and ligands on thiol modification. Journal of Biological Chemistry 266(16): 10260-7

The kinetics of Klebsiella aerogenes urease inactivation by disulfide and alkylating agents was examined and found to follow pseudo-first-order kinetics. Reactivity of the essential thiol is affected by the presence of substrate and competitive inhibitors, consistent with a cysteine located proximal to the active site. In contrast to the results observed with other reagents, the rate of activity loss in the presence of 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) saturated at high reagent concentrations, indicating that DTNB must first bind to urease before inactivation can occur. The pH dependence for the rate of urease inactivation by both disulfide and alkylating agents was consistent with an interaction between the thiol and a second ionizing group. The resulting macroscopic pKa values for the 2 residues are less than 5 and 12. Spectrophotometric studies at pH 7.75 demonstrated that 2,2'-dithiodipyridine (DTDP) modified 8.5 +/- 0.2 mol of thiol/mol of enzyme or 4.2 mol of thiol/mol of catalytic unit. With the slow tight binding competitive inhibitor phenyl-phosphorodiamidate (PPD) bound to urease, 1.1 +/- 0.1 mol of thiol/mol of catalytic unit were protected from modification. PPD-bound DTDP-modified urease could be reactivated by dialysis, consistent with the presence of one thiol per active site. Analogous studies at pH 6.1, using the competitive inhibitor phosphate, confirmed the presence of one protected thiol per catalytic unit. Under denaturing conditions, 25.5 +/- 0.3 mol of thiol/mol of enzyme (Mr = 211, 800) were modified by DTDP.

US$29.90

PMID: 2037578


Other references

Murali, N.; Ravin, H., 1990: Farm level advisory and monitoring systems in Denmark: a case study on field pea. Proceedings of the 3rd International Conference on Computers in Agricultural Extension Programs Fedro S Zazueta editor January 31 February 1-1990 Grosvenor Resort Hotel Disney World Village Lake Buenavista FL: 587

Post W., 1990: Nest survival in a large ibis heron colony during a three year decline to extinction. I studied nest survival of seven species of Ciconiiformes on a dredge-spoil island in South Carolina, USA. In 1984, about 24,450 pairs nested in the colony. By 1986, only 3,682 pairs remained, and the site was abandoned in 1987. White Ibis (Eudoci...

Gordon, Isabella, 1930: Seven new species of Brachyura from the coasts of China. Oxyrhyncha: Pu-gettia cristata [female] (p. 520); P sagamiensis (p. 521) is based upon a Japanese specimen described by Parisi in 1915 under the name of P. brevirostris Doflein. Brachyrhyncha: Neptunus (Hellenus) alcocki (p. 521), based upon speci...

Hiragun, M.; Hiragun, T.; Oseto, I.; Uchida, K.; Yanase, Y.; Tanaka, A.; Okame, T.; Ishikawa, S.; Mihara, S.; Hide, M., 2016: Oral administration of β-carotene or lycopene prevents atopic dermatitis-like dermatitis in HR-1 mice. NlmCategory="UNASSIGNED">Atopic dermatitis (AD) is a chronic relapsing eczematous skin disease. Certain populations of patients are resistant to standard therapies with topical steroids and/or calcineurin inhibitors, and require syste...

Iversen, R.R., 1998: Occupational social work for the 21st century. Economic restructuring and radical changes in welfare policy are causing increasingly severe employment dislocation and disadvantage among many urban residents, particularly women, members of racial and ethnic minority groups, and youths. Despite...

Cartwright, T.C.; Brown, J.E.; Thomas, R.C., 1971: Combining breeds to increase 180-day calf weight. Weights at 180 days of age were collected on 2533 calves involving the Charolais and Charbray, Brahman, Hereford, Santa Gertrudis (SG), Red Poll (RP) and Brown Swiss (BS) breeds. The data were analysed using least-squares procedures with breed, ye...

Takeda, G.; Udagawa, T., 1976: Ecological studies on the photosynthesis of winter cereals part 3 changes of the photosynthetic ability of various organs with growth. Changes with growth in photosynthetic ability of various organs, such as leaf blades, leaf sheaths, culms (parts without leaf sheaths) and ears of barley, wheat, oat and rye plants sown in autumn were measured during 1969-74. Photosynthetic rates...

Lemee G., 1983: Old and present erosion on the sandy slopes of Fontainebleau. Bulletin d'Ecologie 14(2): 87-97

Verosub K.L.; Tchernov E., 1991: Preliminary results of the magnetostratigraphic study of a sedimentary sequence with lithic industry in Israel. Actes du

Lee, E.; Ryu, G.Ryul.; Ko, S-Hyun.; Ahn, Y-Bae.; Song, K-Ho., 2017: A role of pancreatic stellate cells in islet fibrosis and β-cell dysfunction in type 2 diabetes mellitus. To investigate whether the activation of pancreatic stellate cells (PSCs) leads to pancreatic β-cell dysfunction in type 2 diabetes mellitus (T2DM). The pancreases of Otsuka Long-Evans Tokushima Fatty (OLETF) rats, an animal model of T2DM, and pa...