Inactivation mechanism of the beta-ketoacyl-[acyl carrier protein] reductase of bacterial type-II fatty acid synthase by epigallocatechin gallate.
Epigallocatechin gallate (EGCG), a major compound from green tea, reversibly inhibits beta-ketoacyl-[acyl carrier protein] reductase (FabG) from Escherichia coli. In this study, we found that EGCG exhibited an atypical time-dependent inhibition of FabG, which possibly resulted from the EGCG-induced aggregation of FabG. It was observed that FabG inactivation and aggregation occurred nearly simultaneously, with a lag time that decreased with increasing EGCG concentration. These results suggest that some chemical reactions, required for aggregation and inactivation, occurred during the lag time. Since EGC was detected by HPLC after the incubation of EGCG with FabG, EGCG probably covalently modified FabG. These further results showed that 1 tetramer of FabG must be modified by several, possibly 4, EGCG molecules before the formation of FabG aggregates. FabG aggregation was a first-order reaction independent of protein concentration. Due to an initial lag time, the first-order rate of aggregation gradually increased, reaching a maximal and constant value. The effect of increasing concentration of EGCG on the first-order rate constant for aggregation indicated that EGCG bound to FabG by affinity labeling. Based on the results, we propose a mechanism for the interaction of EGCG with FabG:EGCG first binds reversibly to each subunit of FabG, followed by covalent modification and then aggregation of the 4 EGCG-modified subunits.
Li
Bing-Hui
BH
Department of Biology, Graduate University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
Zhang
Rui
R
Du
Ya-Tao
YT
Sun
Ying-Hui
YH
Tian
Wei-Xi
WX
D064431:3-Oxoacyl-(Acyl-Carrier-Protein) Reductase; D000123:Acetyltransferases / Q000037:antagonists & inhibitors*; D000429:Alcohol Oxidoreductases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors; D002392:Catechin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D011232:Chemical Precipitation; D054889:Fatty Acid Synthase, Type II; D064429:Fatty Acid Synthases / Q000037:antagonists & inhibitors*; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D011480:Protease Inhibitors / Q000494:pharmacology; D011485:Protein Binding; D013997:Time Factors
D001426:Bacterial Proteins; D009097:Multienzyme Complexes; D011480:Protease Inhibitors; D002392:Catechin; C045651:epigallocatechin gallate; D000429:Alcohol Oxidoreductases; D064431:3-Oxoacyl-(Acyl-Carrier-Protein) Reductase; D000123:Acetyltransferases; D064429:Fatty Acid Synthases; D054889:Fatty Acid Synthase, Type II