Purification, physicochemical, and kinetic properties of liver acetyl- CoA:arylamine N-acetyltransferase from rapid acetylator rabbits

HH Andres, RS Vogel, GE Tarr, L Johnson and WW Weber

Cytosolic liver acetyl-CoA:arylamine N-acetyltransferase (EC 2.3.1.5) from homozygous rapid acetylator rabbits (strain III/J) was purified to homogeneity as judged by gel filtration sodium dodecyl sulfate- polyacrylamide disc gel electrophoresis and isoelectrofocusing. The isoelectric point was estimated to be 5.2. The molecular weight was determined to be 33,500 by sodium dodecyl sulfate-polyacrylamide disc gel electrophoresis and 33,000 by Sephacryl S-200 gel filtration. The amino acid composition is reported and 16 tryptic peptides were sequenced by Edmann degradation, including a peptide from which a very specific oligonucleotide probe can be synthesized. The enzyme contained neither amino sugars nor cofactors. A broad pH optimum from pH 5.9 to 8.6 was observed. N-Acetyltransferase activity showed a strong dependency on the salt concentration. From the influence of the basicity of the acceptor amine on the maximum velocity, it was concluded that the formation of the covalent acetyl-enzyme intermediate is the rate-limiting step in the N-acetyltransferase-catalyzed acetylation of amines. The covalent intermediate reacts, then, in a fast step with the acceptor amine, when using aniline derivatives with pKa values ranging from 5.65 to 1.74. However, with the weakly basic 4- nitroaniline, the acetyltransfer from the catalytic intermediate to the amine seems to be rate-limiting. A structure-activity study of 30 aniline derivatives that differ in hydrophobicity, position, size, charge, and number of substituents showed that some ortho-substituted derivatives were not acetylated.

Volume 31, Issue 4, pp. 446-456, 04/01/1987
Copyright © 1987 by American Society for Pharmacology and Experimental Therapeutics

This article has been cited by other articles:

				D. W. Hein, C. A. McQueen, D. M. Grant, G. H. Goodfellow, F. F. Kadlubar, and W. W. Weber Pharmacogenetics of the Arylamine N-Acetyltransferases: A Symposium in Honor of Wendell W. Weber Drug Metab. Dispos., April 13, 2001; 28(12): 1425 - 1432. [Abstract] [Full Text]