Kinetic studies on enzymatic acetylation of chloramphenicol in Streptococcus faecalis

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Abstract
The kinetics of chloramphenicol (CP) acetylation by CP acetyltransferase from Streptococcus faecalis was studied. CP was shown to be acetylated enzymatically to its 3-O-acetyl derivative (3-AcCP) in the presence of acetyl coenzyme A, after which 3-AcCP was converted nonenzymatically to its 1-O-acetyl isomer, 1-O-acetyl CP (1-AcCP). At equilibrium, the 1-AcCP and 3-AcCP were present in a 1:4 ratio. Subsequently the diacetylated product, 1,3-O-O-diacetyl CP [1,3-(Ac)2CP], was enzymatically produced from 1-AcCP by the same enzyme. Theoretical calculation of rate constants (k1, k2, k3) for each successive reaction is as follows: (Formula: see text). This calculation gave k1 = 0.4 min-1, k2 = 0.002 min-1, and k3 = 0.016 min-1. Experimental results agreed closely with these calculated values. Images