Illuminating the binding interactions of galactonoamidines during the inhibition of β-galactosidase (E. coli)

Bioorganic & Medicinal Chemistry

Fan

2016

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Aiming at the development of potent inhibitors of -glucosidases, a small library of galactonoamidines and one arabinoamidine derived in analogy were studied as inhibitors of sweet almond -glucosidase. The five-membered glycon in arabinoamidine was shown to interact with the proton donor in the active site of the retaining enzyme, but not with the nucleophile. By contrast, the corresponding galactonoamidine with a six-membered glycon and identical aglycon interacts with both hydrolysis-promoting amino acids in the active site and inhibits the enzymatic hydrolysis of -glucosides in the low nanomolar concentration range. While both inhibitors are competitive, their inhibition ability is more than 37,000-fold different.

Section: Resultssupporting

confidence: 72%

“…6,8–10 All members of the library were characterized as competitive inhibitors, while selected galactonoamidines displayed inhibition constants in the nano- and picomolar concentration range placing them among the most potent inhibitors of glycosidases known today. 8,11 …”

Section: Introductionmentioning

confidence: 99%

Arabinoamidine synthesis and its inhibition toward β-glucosidase (sweet almonds) in comparison to a library of galactonoamidines

Bioorganic & Medicinal Chemistry

Fan

2016

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“…The compounds were previously synthesized in this laboratory and characterized as potent competitive inhibitors of β-galactosidase (E. coli) in an unrelated study. 39 For potent inhibition of the enzymatic hydrolysis, significant H-bond donor and acceptor interactions were identified at the hydroxyl groups in the glycon of 1 at C-2, and, to some lesser extent, at C-4 revealing the binding sites in the active site of the natural catalyst. 39 Considering the reported acidity of hydroxyl groups in carbohydrates upon coordination to metal ions, 47 deprotonation and binding sites at the hydroxyl groups at C-2, C-3, C-4 and/or C-6 of the glycon may be identified with decreasing binding strength in the given order.…”

Section: Identifying Putative Binding Sites In Galactonoamidine Upon mentioning

confidence: 99%

Discrimination of chiral copper(ii) complexes upon binding of galactonoamidine ligands

2016

Dalton Trans.

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The coordination between N-p-methylbenzyl-d-galactonoamidine, a putative transition state analogue of the hydrolyis of glycosidic bonds, and symmetric and chiral binuclear copper(ii) complexes was characterized by spectroscopic titration, isothermal titration calorimetry, circular dichroism spectroscopy, and DFT calculations to elucidate the binding sites in the carbohydrate upon coordination to selected metal complexes. For the formation of metal complex-glyconoamidine assemblies, contributions of the amidine site and of the hydroxyl group at C-2 in the glycon of the amidine are noted. The chiral complexes S- and R-Cubpdbo are discriminated by a third binding site in the carbohydrate that leads to higher stability of complexes derived from S-Cubpdbo (4-5 kcal mol) compared to those formed from R-Cubpdbo.

“…Similar conclusions on inhibitor binding in presence of steric hindrance were also previously reported by us and others. [ 39 – 41 ] Additionally, the frequency of H-bond interactions between β -galactosidase (bovine liver) and galactonoamidine 1v is only slightly smaller than for 1a ( Figure 5b ). As 1x is a control compound lacking the aglycon of 1a and 1v , the corresponding aglycon binding site remains unoccupied ( Figure 5C ), and the loop closure is incomplete.…”

Section: Resultsmentioning

confidence: 94%

Picomolar inhibition of β-galactosidase (bovine liver) attributed to loop closure

Wang

Bioorganic & Medicinal Chemistry

2017

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In an effort to examine similarities in the active sites of glycosidases within the GH35 family, we performed a structure-activity-relationship study using our recently described library of galactonoamidines. The kinetic evaluation based on UV/Vis spectroscopy disclosed inhibition of β-galactosidase (bovine liver) in the picomolar concentration range indicating significantly higher inhibitor affinity than previously determined for β-galactosidase (A. oryzae). Possible alterations in the secondary protein structure or folding were excluded after further examination of the inhibitor binding using CD spectroscopy. Molecular dynamics studies suggested loop closing interactions as a rationale for the disparity of the active sites in the β-galactosidases under investigation.