Coenzyme B12-dependent glutamate mutase catalyses the interconversion of (2S)-glutamic acid and (2S, 3S)-3-methylaspartic acid. The enzyme is unable to accept alternative substrates for the rearrangement reaction but is inhibited by substrates analogues including (2S, 3R)- and (25, 3S)- and (2S, 3S)-3-methylglutamic acid, 2-bromo-2, 3-methanosuccinic acid, (2S)-homocysteic acid. The primary isotope effect uponVmax andV/K for the isomerisation of the (2S)-glutamic acid is 3.7 ± 0.2 and 13.5 ± 1.0 respectively. There are two C-H bond breaking steps involved in the isomerization reaction. The relative sizes ofDV andD(V/K) indicate that neither of these steps are cleanly rate limiting.
