ESCHERICHIA COLI K-12*

~~~~~~~c~t;;m~+C~+ NAY-+ 3 and D-1-amino-2-propanol dehydrogenase F? D 1 amino-2-propanol + NA&. Each enzyme has been obtained in purified form free of the other; the nature of the reaction catalyzed by the latter dehydrogenase alone and in a coupled system with the former enzyme has been studied. The results provide an explanation on the enzymological level for the utilization of L-threonine by cell suspensions of certain microorganisms for the biosynthesis of the D-1-amino-2-propanol moiety of Vitamin B 12'