Coenzyme binding site analog studies

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). 

---