Interactions between coenzyme B12 analogs and adenosylcobalamin-dependent glutamate mutase from Clostridium tetanomorphum.
Adenosylcobalamin (AdoCbl)-dependent glutamate mutase from Clostridium tetanomorphum comprises two weakly-associating subunits, MutS and MutE, which combine with AdoCbl to form the active holo-enzyme. Three coenzyme analogs, methylcobinamide (MeCbi), adenosylcobinamide (AdoCbi) and adeosylcobinamide-GDP (AdoCbi-GDP), were synthesized at milligram scale. Equilibrium dialysis was used to measure the binding of coenzyme B(12) analogs to glutamate mutase. Our results show that, unlike AdoCbl-dependent methylmalonyl CoA mutase, the ratio k(cat)/K(m) decreased approximately 10(4)-fold in both cases when AdoCbi or AdoCbi-GDP was used as the cofactor. The coenzyme analog-binding studies show that, in the absence of the ribonucleotide tail of AdoCbl, the enzyme's active site cannot correctly accommodate the coenzyme analog AdoCbi. The results presented here shed some light on the cobalt-carbon cleavage mechanism of B(12).
Chen
Hao-Ping
HP
Institute of Biotechnology, National Taipei University of Technology, Taiwan. hpchen@ntut.edu.tw
Hsu
Huei-Ju
HJ
Hsu
Fang-Ciao
FC
Lai
Chien-Chen
CC
Hsu
Chun-Hua
CH
Hsu
Chung-Hua
CH
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D048012:Clostridium tetanomorphum / Q000201:enzymology*; D003038:Cobamides / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D003956:Dialysis; D019751:Intramolecular Transferases / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011485:Protein Binding; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
D001426:Bacterial Proteins; D003038:Cobamides; D019751:Intramolecular Transferases; C021570:methylaspartate mutase; C000913:cobamamide