Dissociation of branched-chain alpha-keto acid dehydrogenase kinase (BDK) from branched-chain alpha-keto acid dehydrogenase complex (BCKDC) by BDK inhibitors.
Branched-chain alpha-keto acid dehydrogenase kinase (BDK) phosphorylates and inactivates the branched-chain alpha-keto acid dehydrogenase complex (BCKDC), which is the rate-limiting enzyme in the branched-chain amino acid catabolism. BDK has been believed to be bound to the BCKDC. However, recent our studies demonstrated that protein-protein interaction between BDK and BCKDC is one of the factors to regulate BDK activity. Furthermore, only the bound form of BDK appears to have its activity. In the present study, we examined effects of BDK inhibitors on the amount of BDK bound to the BCKDC using rat liver extracts. The bound form of BDK in the extracts of liver from low protein diet-fed rats was measured by an immunoprecipitation pull down assay with or without BDK inhibitors. Among the BDK inhibitors. alpha-ketoisocaproate, alpha-chloroisocaproate, and a-ketoisovalerate released the BDK from the complex. Furthermore, the releasing effect of these inhibitors on the BDK appeared to depend on their inhibition constants. On the other hand, clofibric acid and thiamine pyrophosphate had no effect on the protein-protein interaction between two enzymes. These results suggest that the dissociation of the BDK from the BCKDC is one of the mechanisms responsible for the action of some inhibitors to BDK.
Murakami
Taro
T
Department of Materials Science, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
Matsuo
Masayuki
M
Shimizu
Ayako
A
Shimomura
Yoshiharu
Y
D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide) / Q000378:metabolism*; D000818:Animals; D002208:Caproates / Q000494:pharmacology; D018753:Diet, Protein-Restricted; D045782:Hemiterpenes; D006843:Hydrocarbons, Chlorinated; D007163:Immunosorbent Techniques; D007651:Keto Acids / Q000494:pharmacology; D008099:Liver / Q000201:enzymology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats
D002208:Caproates; D045782:Hemiterpenes; D006843:Hydrocarbons, Chlorinated; D007651:Keto Acids; D047428:Protein Kinase Inhibitors; C036533:2-chloroisocaproic acid; C001505:alpha-ketoisovalerate; C013082:alpha-ketoisocaproic acid; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D011494:Protein Kinases; C035627:(3-methyl-2-oxobutanoate dehydrogenase (lipoamide)) kinase