Allosteric inhibition of human liver aldehyde dehydrogenase by the isoflavone prunetin

作者：Sheikh S; Weiner H

来源：Biochemical Pharmacology, 1997, 53(4): 471-478.

DOI：10.1016/S0006-2952(96)00837-4

• aldehyde dehydrogenase
• prunetin
• isoflavone
• allosteric
• kinetics

Isoflavonoid derivatives including prunetin (4',5-dihydroxy-7-methoxyisoflavone) were shown to be potent inhibitors of human aldehyde dehydrogenases (Keung W-M and Vallee BL, Proc Natl Acad Sci USA 90: 1247-1251, 1993). The inhibition reaction was reinvestigated using recombinantly expressed human aldehyde dehydrogenases. The kinetic analyses showed that prunetin inhibits competitively against both NAD and propionaldehyde with mitochondrial and cytoplasmic enzymes. The K-i value for the mitochondrial enzyme was much lower than for the cytoplasmic enzyme. A mixed pattern of inhibition was obtained with the mitochondrial enzyme in the presence of Mg2+. Only one mole of prunetin binds per mole of tetrameric mitochondrial enzyme, which remains unaltered in the presence of Mg2+. Prunetin did not displace NADH from the enzyme-NADH complex. Propionaldehyde did not reverse the loss of fluorescence obtained due to enzyme-prunetin complex formation, indicating that prunetin may not be interacting at the substrate site. The esterase activity of the mitochondrial enzyme was also inhibited by prunetin in a competitive manner. The replacement of lysine 192 by glutamine resulted in a mutant with a 20% k(cat) and a 100-fold increase in the K-m for NAD compared with the native enzyme. However, the K-i value of prunetin against NAD was similar to that observed with the native enzyme. Prunetin, even at a very high concentration, was not an inhibitor of alcohol and malate dehydrogenase. It was concluded that prunetin may act as an allosteric inhibitor of aldehyde dehydrogenase.

• 出版日期1997-2-21