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Identification of a paramagnetic species as an early intermediate in the coenzyme B 12 ‐dependent glutamate mutase reaction A cob(II)amide?
Author(s) -
Leutbecher U.,
Albracht S.P.J.,
Buckel W.
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80754-5
Subject(s) - adenosylcobalamin , dithiothreitol , mutase , cofactor , chemistry , electron paramagnetic resonance , substrate (aquarium) , glutamate receptor , amide , enzyme , biochemistry , stereochemistry , nuclear magnetic resonance , biology , ecology , physics , receptor
Highly active and cobamide‐free glutamate mutase was obtained from Clostridium cochlearium by a modification of the original purification procedure. After incubation of the enzyme with dithiothreitol, adenosylcobalamin (coenzyme B 12 ) and the substrate ( S )‐glutamate, a paramagnetic species was observed by EPR‐spectroscopy. The signal was maximal within 15 ms after mixing with glutamate. Different signals were detected after incubating the system with the competitive inhibitors (2 S ,4 S )‐4‐fluoroglutamate or 2‐methyleneglutarate instead of the substrate. The former developed with an at least 100‐fold lower rate then the signal with glutamate. All three signals are probably due to low‐spin cob(II)amide species with an extraordinary low g xy value as compared with cob(II)alamin.