Specificity of lipoamide dehydrogenase for alpha-keto acid dehydrogenase complexes and the glycine cleavage system.
Rat liver lipoamide dehydrogenase (LipDH) was separated into three types on DE-32 column chromatography, but no difference was observed among them in either immunological reactivity or enzymatic properties. A reconstitution experiment of branched-chain alpha-keto acid dehydrogenase complex (BCKADH) revealed that the most anionic type of LipDH was the most effective for the enzyme complex while the three types of LipDH were the same in the affinity for BCKADH subcomplex. All three types of LipDH were equally effective in reconstituting pyruvate dehydrogenase complex, alpha-ketoglutarate dehydrogenase complex and the glycine cleavage system. However, either pyruvate dehydrogenase or alpha-keto-glutarate dehydrogenase complex appeared to involve a certain LipDH in vivo which was firmly integrated into and hardly dissociable from the complex. A broad specificity of LipDH was observed for the glycine cleavage system. When BCKADH reconstitution experiments were carried out with both LipDHs from various sources and purified rat liver BCKADH subcomplex, the effectiveness of animal LipDHs was proportional to the extent of their immunological reactivity to the anti-rat LipDH antibody. However, BCKADH activity was also restored by a certain bacterial LipDH which had no cross-reactivity with the antibody, and LipDHs from some bacterial species, which reacted well with the antibody, showed no effect for the reconstitution of BCKADH. Thus, the determinant(s) of LipDH for the integration into alpha-keto acid dehydrogenase complexes including BCKADH can be its tertiary and/or quarternary structure rather than its primary and secondary structures.
Hakozaki
M
M
Department of Biochemistry I, Fukushima Medical College, Japan.
Honda
K
K
D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D000818:Animals; D008058:Dihydrolipoamide Dehydrogenase / Q000737:chemistry / Q000378:metabolism*; D005998:Glycine / Q000378:metabolism*; D006801:Humans; D007658:Ketone Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism*; D051381:Rats
D009097:Multienzyme Complexes; D007658:Ketone Oxidoreductases; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D008058:Dihydrolipoamide Dehydrogenase; D005998:Glycine