Studies of the Intermediate Products Formed During the Hydrolysis of Urea by Urease

Sumner, James B.; Hand, David B.; Holloway, R. Grant

doi:10.1016/s0021-9258(18)76617-9

Cited by 29 publications

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“…The previous work of Sumner et al (1931) at pH ~9 showed the formation of appreciable amounts of carbamate in the enzyme-catalyzed hydrolysis of urea. However, at worst, carbamate would have a half-life of less than 10 sec under the conditions of these workers in the absence of ammonia.…”

Section: Discussionmentioning

confidence: 92%

“…We have therefore reexamined the inhibition of jack bean urease by hydroxamic acids and the initial results of these investigations are reported in this paper. Sumner et al (1931) first convincingly demonstrated the absence of cyanate and the formation of ammonium carbamate in the products of the urease-catalyzed hydrolysis of urea. Sumner stated: "There is no reason to doubt that ammonium carbamate is an intermediate product of the action of urease on urea, but it is not necessarily the first intermediate product."…”

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confidence: 99%

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Jack bean urease (EC 3.5.1.5). Demonstration of a carbamoyl-transfer reaction and inhibition by hydroxamic acids

Blakeley¹,

Hinds²,

Kunze³

et al. 1969

Biochemistry

138

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A carbamoyl-transfer reaction has been demonstrated in the urease-catalyzed hydrolysis of urea, using a thymol blue buffer to give a sensitive spectrophotometric measure of acidity changes. This demonstration offers further support for the proposition that carbamate is the first product of the urease-catalyzed hydrolysis of urea. The inhibition of urease by aceto-Jack bean urease (urea amidohydrolase, EC 3.5.1.5) has a cherished place in the enzymologist's heart, since it was responsible for the death blow to the proposition that the protein was merely a carrier of the catalytic species (Northrop, 1961). Nonetheless, the enzyme remains ill understood and is deserving of a detailed and intensive mechanistic attack. Sumner (1951) described urease as "absolutely specific" and until recently only two additional substrates, hydroxyurea and dihydroxyurea, have been

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Section: Discussionmentioning

confidence: 92%

mentioning

confidence: 99%

Jack bean urease (EC 3.5.1.5). Demonstration of a carbamoyl-transfer reaction and inhibition by hydroxamic acids

Blakeley¹,

Hinds²,

Kunze³

et al. 1969

Biochemistry

138

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“…Although ammonium carbamate is formed under the conditions of the assay (c/. Sumner et al, 1931), its decomposition is not rate limiting (Roughton, 1941;Jensen, 1959). This is attested to by the fact that the rate is linear in enzyme concentration (see below).…”

Section: Resultsmentioning

confidence: 99%

Jack bean urease (EC 3.5.1.5). A new purification and reliable rate assay

Blakeley¹,

Webb²,

Zerner³

1969

Biochemistry

120

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“…The mechanism of action of the metalloenzyme urease has been a subject of discussion for many years. − Although considerable progress has been made toward providing a thorough understanding of this enzyme, many questions still remain about the precise geometry by which urea binds to the dinickel center, the interactions between the substrate and the active site residues, and the nature of the hydrolytic attack but there is no evidence that it is the first intermediate formed in the reaction.…”

Section: Discussionmentioning

confidence: 99%

Decomposition of Alkyl-Substituted Urea Molecules at a Hydroxide-Bridged Dinickel Center

Barrios

Lippard

2001

Inorg. Chem.

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The interactions between N-methylurea, N,N'-dimethylurea, N,N-dimethylurea, tetramethylurea, and thiourea and the hydroxide-bridged dinickel complex [Ni(2)(mu-OH)(mu-H2O)(bdptz)(H2O2](OTs)(3) were investigated. Structural characterization of [Ni(2)(mu-OH)(mu-H2O)(bdptz)(Me-urea)(CH3CN)](ClO4)(3) (1) and [Ni(2)(mu-OH)(mu-H2O)(bdptz)(thiourea)(CH3CN)](ClO4)(3) (2) provided insight into the interactions of the substrates with the dinickel center. In 1, the methylurea molecule coordinates to the dinickel complex through its carbonyl oxygen atom. Complex 2 has a similar geometry, with the thiourea molecule bound to a nickel ion through its sulfur atom. When the urea substrates are heated in the presence of the hydroxide-bridged dinickel complex, N-methylurea and N,N-dimethylurea react to form methylammonium cyanate and dimethylammonium cyanate, respectively. After long reaction times, thiourea reacts similarly, producing ammonium thiocyanate. The other substrates are unreactive. These results indicate that the dinickel complex promotes the elimination of alkylamines from urea substrates to form cyanate but cannot effect the direct hydrolysis of such substrates.

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Studies of the Intermediate Products Formed During the Hydrolysis of Urea by Urease

Cited by 29 publications

References 0 publications

Jack bean urease (EC 3.5.1.5). Demonstration of a carbamoyl-transfer reaction and inhibition by hydroxamic acids

Jack bean urease (EC 3.5.1.5). Demonstration of a carbamoyl-transfer reaction and inhibition by hydroxamic acids

Jack bean urease (EC 3.5.1.5). A new purification and reliable rate assay

Decomposition of Alkyl-Substituted Urea Molecules at a Hydroxide-Bridged Dinickel Center

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