The enzymatic acetylation of amines.

The enzymatic acetylation of aromatic amines (1, Z), choline (3), glucosamine (4), and histamine (5) has been shown to require coenzyme A (CoA) ; recent studies (6) have demonstrated that the thio ester, acetyl CoA, can serve as the acetyl donor in the acetylation reaction. However, more detailed studies on the properties of the acetylating enzyme were made difficult by the absence of a suitable method for following the acetylation reaction continuously. In the work reported here, a convenient, direct spectrophotometric method was used for following the acetylating reaction, which depended on the marked difference between the absorption spectra of free and acylated aromatic amines previously used in the study of the hydrolysis of formylkynurenine (7). Most of the studies were carried out with p-nitroaniline, as the changes in absorption produced by acetylation could be measured above 400 mM; this wave-length is sufficiently high so that interference from the extraneous absorption commonly found in tissue extracts is largely avoided. With purified enzyme preparations the spectrophotometric method can also be used with a variety of other compounds. Using the spectrophotometric method, we have studied acetylation of amines by acetyl CoA, the sulfhydryl nature of the acetylating enzyme, and inhibition of the acetylation reaction by free CoA.