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KMID : 0380219930260020105
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Journal of Biochemistry and Molecular Biology
1993 Volume.26 No. 2 p.105 ~ p.113
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Reaction Mechanism of Chloramphenicol Acetyltransferase
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Young-Kweon Cho
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Abstract
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Initial velocity, product inhibition and dead-end inhibition patterns
suggest tat chloramphenicol acetyltransferase catalyzes its reaction by a
rapid equilibrium radnom mechanism, wherein the interconcversion of
central complex is a rate-limiting step in both forward and reverse
ractions. The results from chemical modification and rectant protection
experiments suggest that histdine and aspartic actid may be inolved in
cagtalysis and cysteine in the binding of acetyl CoA. Above proposal
was confirmed further by ph dependence of the kinetic parameters. the
data from pH study suggest that N1-OH of histidine hydroge-bonded to
aspartic acid accepts froton from hydroxyl group of C3 of
chloramphenicol concomitant with nuclephilic attack of the acetyl group
barbon on cetyl-CoA. the proton in N3 of histidine is then transfered tro
-S-Coa. taken together, the above results stongly suggest that
chloramphenicol acetyltransferase catalyzes its reaction via general
acid-base catalysis using a single base as a porton shuttle.
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