Abstract
The characteristics and kinetic properties of an N-acetyltransferase have been studied in partially purified preparations from rabbit liver. The enzyme catalyzes the acetylation of isonicotinic acid hydrazide, sulfadiazine, sulfamerazine, sulfamethazine, and sulfanilamide. A "ping-pong Bi-Bi" mechanism, which involves the formation of an acetylated enzyme, is proposed for the acetylation of INH from our studies of initial velocity patterns and product inhibition. The possible limitations of the Michaelis constant (Km) as a means of characterizing an enzyme which catalyzes "ping-pong Bi-Bi" reactions or other reactions involving two or more substrates and two or more products are noted.
ACKNOWLEDGMENTS We wish to thank Dr. B. N. La Du for his advice throughout these studies. This investigation was supported in part by U. S. Public Health Service Grant AM 08577 from the National Institutes of Health.
- Copyright ©, 1967, by Academic Press Inc.
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