Mechanism of the irreversible inhibition of aspartate aminotransferase by the bacterial toxin L-2-amino-4-methoxy-trans-3-butenoic acid.

Rando, Robert R.; Relyea, Noël M.; Cheng, Lydia

doi:10.1016/s0021-9258(17)33438-5

Cited by 53 publications

(11 citation statements)

References 16 publications

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“…Since the second term on the right side of eq 2 is common for the two pathways, it is sufficient to compare the total energy for 7 and 8. The total energies for these compounds were calculated as -4520.19 and -4518.04 eV, respectively, predicting that the pathway via transamination is energetically favorable by 49 kcal/mol (1 eV = 23 kcal/mol), and this supports the mechanism proposed by Rando et al 21 Similarly, the total energy for the transaminated product of vinylglycine is calculated as -3782.10 eV, and this is more stable than the isomerized product by 38 kcal/mol. This seems to be in contradiction with the experimental finding that vinylglycine undergoes an isomerization reaction almost exclusively.21,22 However, this is not necessarily the case, because isomerization of vinylglycine occurs only when Al3+ is added in the reaction mixture, and when Al3+ was omitted the transamination occured almost exclusively.21 This means that the occurrence of a transamination reaction is easier than isomerization in the absence of Al3+, in agreement with the calculated total energy.…”

Section: Resultssupporting

confidence: 82%

“…Based on the data of the irreversible inactivation of aspartate aminotransferase by 2-keto-4methoxy-írons-3-butenoic acid and also from the model studies on the transamination or/and isomerization of AMB by pyridoxal, Rando et al proposed that inactivation of aminotransferase by AMB would occur via a transamination process. 21 In this article, it is attempted to predict theoretically which pathway in Scheme II is more preferable by com-Scheme II H 8 paring energy increments for these two reaction pathways. Since the second term on the right side of eq 2 is common for the two pathways, it is sufficient to compare the total energy for 7 and 8.…”

Section: Resultsmentioning

confidence: 99%

“…Although the nucleophile involved in the covalent binding is not identified, it is sure that one of the electronegative atoms, such as O, S, and N, is involved. 21 The HOMO of the nucleophilic groups -O' of serine and -S" of cysteine are calculated as -3.18 and -3.40 eV, respectively. It is worth noting that these values are higher 6.920-N _-1.589 The HOMO and LUMO calculated by the CNDO/2 method for aspartate (14) and its pyridoxal-linked state (15).…”

Section: Resultsmentioning

confidence: 99%

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Molecular orbital study on the reaction mechanism of irreversible enzyme inhibitors

Nagata¹,

Yamaguchi²

1979

J. Med. Chem.

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By means of the molecular orbital method, the reaction mechanism of the specific and irreversible enzyme inhibitors, such as cycloserine, L-2-amino-4-methoxy-trans-3-butenoic acid (AMB), and vinylglycine (2-amino-3-butenoic acid), was studied. Firstly, it was attempted to know which pathway is probable between the transamination process and the isomerization one. By comparing the energy increments for these two reactions, the transamination reaction was predicted to be energetically favorable, supporting the proposition of Rando. Upon complexing with the coenzyme-pyridoxal moiety of alanine racemase or aminotransferase, the reactivity of the inhibitors toward the nucleophile was found to be considerably increased due to the lowering of the lowest unoccupied molecular orbital (LUMO), and this was considered to be the reason why the inhibitors become bound with the enzyme irreversibly. The LUMO of aspartate, substrate of aspartate aminotransferase, is higher than those of the inhibitors in the free state, as well as in the pyridoxal-linked state. This difference in the energy of the molecular orbital between substrate and inhibitors was considered to be correlated with the difference in the complex-forming properties of these compounds toward the nucleophile in the enzyme.

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Section: Resultssupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Molecular orbital study on the reaction mechanism of irreversible enzyme inhibitors

Nagata¹,

Yamaguchi²

1979

J. Med. Chem.

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“…IV shows a possible structure of the inactivated species. Rando et al (1976) have studied the inactivation mechanism of aspartate aminotransferase (EC 2.6.1.1) by L-2-amino-4-methoxy-rro«i-3butenoate and proposed that a structure similar to IV shows a triplet absorption band in the range of 350 nm. However, the wavelength is far away from those of absorption bands for L-methionine 7-lyase, even though we take the inherent difference between the two enzymes into consideration: the enzyme-bound pyridoxal-P of active aspartate aminotransferase absorbs at a much lower wavelength (360 nm) than that of L-methionine 7-lyase (420 nm).…”

Section: Resultsmentioning

confidence: 99%

Mechanism-based inactivation of L-methionine .gamma.-lyase by L-2-amino-4-chloro-4-pentenoate

Esaki¹,

Takada²,

Moriguchi³

et al. 1989

Biochemistry

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“…They are relatively unreactive substrate analogues which, once activated, may react in situ with a neighboring functional group and thus inactivate the enzyme. Since these enzyme-activated or /ccat inhibitors (Rando, 1974a;Abeles and Maycock, 1976) rely both on binding and catalytic conversion by the target enzyme, they are highly specific in their action and thus have great potential for in vivo applications.The simplest 0,7-unsaturated amino acid, vinylglycine (CH2==CHCHNH2COOH), has been shown previously to be a kcm inhibitor of cytosolic aspartate aminotransferase (Rando, 1974b) as has its 4-methoxy analogue which is a bacterial toxin (Rando et al, 1976). The present study investigates the mode of inactivation of the cytosolic and the mitochondrial isoenzymes of aspartate aminotransferase by vinylglycine and characterizes the enzyme-inhibitor adducts.…”

mentioning

confidence: 95%

Active-site labeling of aspartate aminotransferases by the β,γ-unsaturated amino acid vinylglycine

Gehring¹,

Rando²,

Christen³

1977

Biochemistry

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The pyridoxal form of both cytosolic and mitochondrial aspartate aminotransferase is irreversibly inactivated consequent to its interaction with the beta,gamma-unsaturated substrate analogue vinylglycine. Per catalytic cycle, 90% of the enzyme molecules are inactivated while 10% escape inactivation by transamination to the pyridoxamine form. In the presence of vinylglycine plus 2-oxoglutarate, inactivation is complete because of retransamination of the pyridoxamine form to the susceptible pyridoxal form. Peptide analyses after inactivation with [1-14C]vinylglycine showed that vinylglycine alkylates the active-site lysine residue 258 which forms the internal aldimine with the coenzyme pyridoxal 5'-phosphate. The coenzyme itself is left intact; resolution of the inactivated enzyme by base or trichloroacetic acid yields pyridoxal-5'-P. The absorption spectrum of the inactivated enzyme (lambdamax 335 nm) suggests that the cofactor is bound as a substituted aldimine. The proposed pathway of alkylation of Lys-258 involves abstraction of the alpha proton from vinylglycine, isomerization to the alpha,beta-unsaturated enamine, and subsequent nucleophilic attack of the epsilon-amino group of the lysyl residue at the beta carbon of the inhibitor. The determination of the amino acid sequence around the coenzyme-binding lysyl residue in the mitochondrial isoenzyme from chicken gave Ala-(epsilon-Pxy)Lys-Asn-Met-(Gly,Leu,Tyr) which is identical with the other mitochondrial transaminases examined so far.

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Mechanism of the irreversible inhibition of aspartate aminotransferase by the bacterial toxin L-2-amino-4-methoxy-trans-3-butenoic acid.

Cited by 53 publications

References 16 publications

Molecular orbital study on the reaction mechanism of irreversible enzyme inhibitors

Molecular orbital study on the reaction mechanism of irreversible enzyme inhibitors

Mechanism-based inactivation of L-methionine .gamma.-lyase by L-2-amino-4-chloro-4-pentenoate

Active-site labeling of aspartate aminotransferases by the β,γ-unsaturated amino acid vinylglycine

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