Protein labeling with boronic acid

Inactivation of alcohol dehydrogenase from yeast with 14C-labeled [3-(3-bromoacetylpyridinio)-propyl]-adenosine pyrophosphate followed by oxidation showed the presence of 1-carboxymethyl histidine66. After inactivation of the enzyme with labeled [3-(4-bromoacetylpyridinio)-propyl]-adenosine pyrophosphate followed by oxidation, S-carboxymethyl cysteine was identified in the protein. In the case of glyceraldehyde-3-phosphate dehydrogenase, treatment with either coenzyme analogue leads to the modification of the cysteine residue. Treatment with [14C]nicotinamide-5-bromo-4-methylimidazole dinucleotide did not reveal any modified amino-acid-residues. The labeled nicotinamide residue split off during the recovery of the inactivated enzyme. Attempts to synthesize an inactivator labeled with a 14C-acetyl residue did not give satisfactory yields. If the enzyme-coenzyme derivative was treated with tritiated sodium boron hydride, tritium could be introduced (Fig. 22). Studies with... 

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