Naslov
On the Importance of Ribose Orientation in the Substrate Activation of the Coenzyme B12-Dependent Mutases

Autori
Durbeej, Bo ; Sandala, Gregory M. ; Bucher, Denis ; Smith, David M. ; Radom, Leo

Izvornik
Chemistry - A European Journal (0947-6539) 15 (2009), 34; 8578-8585

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
density functional theory calculations ; molecular modeling ; enzymes ; radicals ; reaction mechanisms

Sažetak
The degree to which the corrin ring portion of coenzyme B12 can facilitate the H-atom-abstraction step in the glutamate mutase(GM)-catalyzed reaction of (S)-glutamate has been investigated with density functional theory. The crystal structure of GM identifies two possible orientations of the ribose portion of coenzyme B12. In one orientation (A), the OH groups of the ribose extend away from the corrin ring, while in the other orientation (B) the OH groups, especially that involving O3', are instead directed towards the corrin ring. Our calculations identify a sizable stabilization amounting to ca. 30– 40 kJ mol– 1 in the transition structure (TS) complex corresponding to orientation B (TSBCorIm). A much smaller stabilization (5– 10 kJ mol– 1) is observed for the TS complex where the ribose is positioned in orientation A. The observed stabilization in TSBCorIm appears to be the result of favorable interactions involving O3' and the corrin ring, including a C– H• • • O hydrogen bond. We find that the degree of stabilization is not particularly sensitive to the Co– C distance. Our calculations show that any potential stabilization afforded to the H-atom-abstraction step by coenzyme B12 is sensitive to the orientation of the ribose moiety.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija, Biologija

POVEZANOST RADA