Microbial Metabolism of Amino Alcohols. Ethanolamine Catabolism Mediated by Coenzyme B12-dependent Ethanolamine Ammonia-Lyase in Escherichia coli and Klebsiella aerogenes

Abstract

The enzyme responsible for ethanolamine metabolism by E. coli and K. aerogenes, ethanolamine ammonia-lyase, was dependent on vitamin B12. A strong odor of acetaldehyde was noted during growth of each bacterium on glycerol plus ethanolamine medium. The vitamin B12 dependent utilization of ethanolamine may involve its deamination to acetaldehyde, which is further metabolized via acetate or acetyl-CoA. Ethanolamine ammonia-lyases from both bacteria had optimum activity at pH 7.5-8.0; the apparent Km values for ethanolamine and coenzyme-B12 were .apprx. 0.2 mM and 0.1 .mu.M, respectively. Vitamin B12 itself was a potent inhibitor. Enzyme activities of cell extracts of bacteria varied from 100-230 nmol acetaldehyde formed/min per mg protein.