Mechanism and Inhibitor Exploration with Binuclear Mg Ketol-Acid Reductoisomerase: Targeting the Biosynthetic Pathway of Branched-Chain Amino Acids.
Chembiochem
; 21(3): 381-391, 2020 02 03.
Article
in En
| MEDLINE
| ID: mdl-31309701
ABSTRACT
Binuclear Mg ketol-acid reductoisomerase (KARI), which converts (S)-2-acetolactate into (R)-2,3-dihydroxyisovalerate, is responsible for the second step of the biosynthesis of branched-chain amino acids in plants and microorganisms and thus serves as a key inhibition target potentially without effects on mammals. Here, through the use of density functional calculations and a chemical model, the KARI-catalyzed reaction has been demonstrated to include the initial deprotonation of the substrate C2 hydroxy group, bridged by the two Mg ions, alkyl migration from the C2-alkoxide carbon atom to the C3-carbonyl carbon atom, and hydride transfer from a nicotinamide adenine dinucleotide phosphate [NAD(P)H] cofactor to C2. A dead-end mechanism with a hydride transferred to the C3 carbonyl group has been ruled out. The nucleophilicity (migratory aptitude) of the migrating carbon atom and the provision of additional negative charge to the di-Mg coordination sphere have significant effects on the steps of alkyl migration and hydride transfer, respectively. Other important mechanistic characteristics are also revealed. Inspired by the mechanism, an inhibitor (2-carboxylate-lactic acid) was designed and predicted by barrier analysis to be effective in inactivating KARI, hence probably enriching the antifungal and antibacterial library. Two types of slow substrate analogues (2-trihalomethyl acetolactic acids and 2-glutaryl lactic acid) were also found.
Key words
Full text:
1
Database:
MEDLINE
Main subject:
Carboxylic Acids
/
Lactic Acid
/
Enzyme Inhibitors
/
Ketol-Acid Reductoisomerase
/
Amino Acids, Branched-Chain
/
Magnesium
Type of study:
Prognostic_studies
Language:
En
Year:
2020
Type:
Article