Inhibition of Urease by Silver Ions

Ambrose, John F.; Kistiakowsky, G. B.; Kridl, Andrew G.

doi:10.1021/ja01147a106

Cited by 54 publications

(27 citation statements)

References 1 publication

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“…Several other compounds are known to fully or partially inhibit urease, such as acetohydroxamic acid (Kumar and Kayastha 2010a), boric acid (Breitenbach and Hausinger 1988;Reddy and Kayastha 2006), heavy metal ions (Ambrose et al 1951;Kumar and Kayastha 2010b) and the substrate analogues hydroxyurea and methylurea (Gale 1965;Shaw and Raval 1961). However, all have issues with anti-ureolytic effectivity, price, toxicity or chemical stability, which prevents them, at the moment, from being considered as alternatives to some of the established ammonia emission mitigation strategies in agriculture ( …”

Section: Other Anti-ureolytic Compoundsmentioning

confidence: 99%

The molecular processes of urea hydrolysis in relation to ammonia emissions from agriculture

Sigurdarson

Svane

Karring

2018

Rev Environ Sci Biotechnol

237

129

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Ammonia emissions from the agricultural sector give rise to numerous environmental and societal concerns and represent an economic challenge in crop farming, causing a loss of fertilizer nitrogen. Ammonia emissions from agriculture originate from manure slurry (livestock housing, storage, and fertilization of fields) as well as urea-based mineral fertilizers. Consequently, political attention has been given to ammonia volatilization, and regulations of ammonia emissions have been implemented in several countries. The molecular cause of the emission is the enzyme urease, which catalyzes the hydrolysis of urea to ammonia and carbonic acid. Urease is present in many different organisms, encompassing bacteria, fungi, and plants. In agriculture, microorganisms found in animal fecal matter and soil are responsible for urea hydrolysis. One strategy to reduce ammonia emissions is the application of urease inhibitors as additives to urea-based synthetic fertilizers and manure slurry to block the formation of ammonia. However, treatment of the manure slurry with urease inhibitors is associated with increased livestock production costs and has not yet been commercialized. Thus, development of novel, environmentally friendly and cost-effective technologies for ammonia emission mitigation is important. This mini-review describes the challenges associated with the volatilization of ammonia in agriculture and provides an overview of the molecular processes of urea hydrolysis and ammonia emissions. Different technologies and strategies to reduce ammonia emissions are described with a special focus on the use of urease inhibitors. The mechanisms of action and efficiency of the most important urease inhibitors in relation to agriculture will be briefly discussed.

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Section: Other Anti-ureolytic Compoundsmentioning

confidence: 99%

The molecular processes of urea hydrolysis in relation to ammonia emissions from agriculture

Sigurdarson

Svane

Karring

2018

Rev Environ Sci Biotechnol

237

129

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“…With additional nine other cysteine residues, buried in the subunit and accessible only under denaturating conditions, the overall number of cysteines per jack bean subunit amounts to 15, corresponding to 90 cysteines per molecule [18]. Although never shown explicitly by experiment, the inhibition of urease by heavy metal ions has been ascribed by many authors to the reaction of these ions with the -SH group(s) of cysteine residue(s) resulting in the formation of thiolates [19][20][21][22][23]. Other authors, however, are of the opinion that this inhibition is due to loose complexing of the metals by a function other than sulfhydryl, e.g., a histydyl residue [24,25].…”

Section: Introductionmentioning

confidence: 99%

Multi-step analysis of Hg2+ ion inhibition of jack bean urease

Krajewska

Zaborska

Chudy

2004

Journal of Inorganic Biochemistry

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“…Comparison of the value of the cysteic acid content of urease obtained after performic acid oxidation and hydrolysis (Reithel & Robbins, 1967) with thiol-titration data obtained Vol. 159 by using N-ethylmaleimide and Nbs2 as titrants in denaturing media and in peptic digests (Andrews & Reithel, 1970) Studies with N-ethylmaleimide and Nbs2 as titrants (Ambrose et al, 1951;Gorin & Chang-Chen Chin, 1965;Andrews & Reithel, 1970) Reithel (1970) for the reaction at pH7.1 (33 thiol groups/molecule reacted, leaving 18% of the original activity). Fig.…”

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confidence: 99%

A convenient method of preparation of high-activity urease from Canavalia ensiformis by covalent chromatography and an investigation of its thiol groups with 2,2'-dipyridyl disulphide as a thiol titrant and reactivity probe

Norris

Brocklehurst

1976

Biochemical Journal

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1. A convenient method ofpreparation ofjack-bean urease (EC 3.5.1.5) involving covalent chromatography by thiol-disulphide interchange is described. 2. Urease thus prepared has specific activity comparable with the highest value yet reported (44.5±1.47kat/kg, Km = 3.32±0.05mM; kcat. = 2.15 x 104±0.05 x 104s-1 at pH7.0 and 38°C). 3. Titration of the urease thiol groups with 2,2'-dipyridyl disulphide (2-Py-S-S-2-Py) and application of the method of Tsou Chen-Lu [(1962) Sci. Sin. 11, 1535-1558 suggests that the urease molecule (assumed to have mol.wt. 483000 and e280=2.84x105 litre-molhl cm-1) contains 24 inessential thiol groups of relatively high reactivity (class-I), six 'essential' thiol groups of low reactivity (class-Il) and 54 buried thiol groups (class-III) which are exposed in 6M-guanidinium chloride. 4. The reaction of the class-I thiol groups with 2-Py-S-S-2-Py was studied in the pH range 6-11 at 25'C (1= 0.1 mol/l) by stopped-flow spectrophotometry, and the analogous reaction of the class-Il thiol groups by conventional spectrophotometry. 5. The class-I thiol groups consist of at least two sub-classes whose reactions with 2-Py-S-S-2-Py are characterized by (a) pKa = 9.1, k = 1.56 x 104M-l'S-1 and (b) pKa = 8.1, k = 8.05 x 102M-1 .-1 respectively. The reaction of the class-II thiol groups is characterized by pKa = 9.15 and k = 1.60x 102M-I s-1. 6. At pH values 7-8 the class-I thiol groups consist of approx. 50 % class-Ia groups and 50 % class-lb groups. The ratio class Ia/class lb decreases as the pH is raised according to a pKa value > approx. 9.5, and at high pH the class-I thiol groups consist of at most 25 % class-Ia groups and at least 75 % class-lb groups. 7. The reactivity of the class-II thiol groups towards 2-Py-S-S-2-Py is insensitive to the nature of the group used to block the class-I thiols. 8. All the 'essential' thiol groups in urease appear to be reactive only as uncomplicated thiolate ions. The implications of this for the active-centre chemistry of urease relative to that of the thiol proteinases are discussed.Urease (EC 3.5.1.5) can be extracted fromjack-bean (Canavalia ensiformis) meal and reproducibly purified to high specific activity by the method of Blakeley et al. (1969a). A chloroform/acetone-dried powder of jack-bean meal is extracted with 30% (v/v) acetone containing 1 % 2-mercaptoethanol at 39°C for 5min. The filtrate is left for 48h at 4°C to provide crystalline material that is then dissolved in buffer, dialysed and further purified by recycling upward-flow gel filtration on Sephadex G-200.We have reported a simple general method (covalent chromatography by thiol-disulphide interchange) for the purification ofthiol enzymes and its application in the immobilization of commercial samples of urease

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Inhibition of Urease by Silver Ions

Cited by 54 publications

References 1 publication

The molecular processes of urea hydrolysis in relation to ammonia emissions from agriculture

The molecular processes of urea hydrolysis in relation to ammonia emissions from agriculture

Multi-step analysis of Hg2+ ion inhibition of jack bean urease

A convenient method of preparation of high-activity urease from Canavalia ensiformis by covalent chromatography and an investigation of its thiol groups with 2,2'-dipyridyl disulphide as a thiol titrant and reactivity probe

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