Ethanol-amine ammonia-lyase

Bandaeian, V., Reed, G. H. (2000) Isotope effects in the transient phases of the reaction catalyzed by ethanol-amine ammonia-lyase determination of the number of exchangeable hydrogens in the enzyme-cofactor complex. Biochemistry 39, 12069-12075. 

About 10 coenzyme Bi2-dependent enzymes are now known (reviewed in References 13,14, and 76 see Table 1) four carbon skeleton mutases (methylmalonyl-CoA mutase (MMCM), glutamate mutase (GM), methylene glu-tarate mutase (MGM), isobutyryl-CoA mutase (ICM) ), diol dehydratase (DD), glycerol dehydratase, ethanol-amine ammonia lyase (EAL), two amino mutases, and Bi2-dependent ribonucleotide reductase. The coenzyme Bi2-dependent enzymes are unevenly distributed in the living world, and MMCM is the only enzyme that is also indispensable in human metabolism. ... 

The nitroxidc (IV) (see Section I) was used as a spin label in connection with a study relevant to vitamin B12 coenzyme, which is of type Co (III)—R (R = 5 -deoxyadenosyl) and thus an analog of IV, but with a different axial group R (193). Compound (IV), which we may abbreviate Co(III) — R, was prepared from a Co(I) precursor Bi2s and R Br, and was found to bind to the enzyme ethanolaminc-ammonia-lyase (in this system ethanol-amine is converted to acetaldehyde). By ESR it was concluded that the active site is relatively close to the enzyme surface (sec also Section V,B). 

Ethanolamine ammonia lyase. EAL converts ethanol-amine to acetaldehyde, with loss of ammonia. EAL depends upon adenosylcobamides, such as coenzyme B12 (3), but a range of other adenosylcobamides are also accepted as cofactors, while cobalamins with /3-ligands other than the 5 -deoxy-5 -adenosyl group (of AdoCbl) are inhibitors. Active EAL is multimeric and has an apparent molecular mass of about 560 600kDa. Similar to the mechanism of DD, a radical mechanism is proposed for the isomerization of the vicinal amino-alcohol substrates (ethanolamine, (/f)- and (5)-aminopropanol) by EAL, starting with the abstraction of an H atom from the C-1 position of the substrates. 

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