Biochemistry: The Chemical Reactions of Living Cells, Volume 2 - D. Metzler 1980

Coenzymes – unique specialized natural reagents
Coenzyme forms of vitamin B12
Stereochemistry of the action of vitamin B12-dependent enzymes

Diol dehydratase acts either on the (S)-isomer of 1,2-propanediol

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or on the (R)-isomer:

(asterisks and crosses indicate the geometry of labeled atoms introduced by special techniques).

In both cases, the reaction proceeds with retention of configuration at C-2 and with stereochemical Specificity [183] with respect to one of the two hydrogen atoms at C-1. The reaction catalyzed by methylmalonyl-CoA mutase also proceeds with retention of configuration at C-2 [184], whereas the glutamate mutase reaction is accompanied by inversion:

In the reaction catalyzed by D-α-Lysine mutase (Table 8-6), a hydrogen atom is transferred from C-5 to C-6 [185]. This reaction requires two Proteins as well as Pyridoxal phosphate, which appears to be directly involved in the amino group transfer. The related enzyme L-β-lysine mutase requires Pyruvate as a cofactor [163].



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