Biochim. biophys. acta 25:451-452.




In experiments reported some years ago the enzyme-catalyzed exchange of the amide group of glutamine and asparagine with 15N ammonia was demonstrated but an exchange of the amide groups of protein bound dicarboxylic amino acids could not be explored owing to the unfavorable experimental conditions1 . Recently the problem of the metabolism of protein-amide groups was approached again with the aid of 14C-labeled amines, such as ethanolamine or cadaverine. Soluble protein fractions obtained from sucrose homogenates (o.2sM) of the livers of guinea pigs, rats, mice, and rabbits by centrifugation at roo,ooo X g were incubated in the presence of Ca++ with the 14C-labeled amines. Appreciable radioactivity was recovered in the proteins precipitated and purified by the method of SIEKEVITZ2 (Table I). The incorporating system was activated by Ca++ but not by Mn++- and Mg++ or other metal ions-a fact which makes it unlikely that we are dealing with the enzyme system responsible for glutamo or asparto-transferase activities

Included in

Biochemistry Commons