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Relationship between substrate activity and pKa value of phenols on sulfotransferase from Eubacterium A-44.

Authors
  • Konishi-Imamura, L
  • Kim, D H
  • Kobashi, K
Type
Published Article
Journal
Biochemistry international
Publication Date
Dec 01, 1992
Volume
28
Issue
4
Pages
725–734
Identifiers
PMID: 1482408
Source
Medline
License
Unknown

Abstract

The relationship between the kinetics of the enzyme activity and the structural features of phenolic donor and of acceptor substrates was investigated with a sulfotransferase from Eubacterium A-44, a human intestinal bacterium. The enzyme catalyzed the transfer of the sulfate group from the sulfate esters of phenol having a lower pKa to phenols having a higher pKa. When the Km values for acceptor substrates were measured at their optimal pH, a linear plot for log10Km versus the pKa with a slope of 0.615 was obtained. In addition, it is considered that the effect of pH on the Km values for the various acceptors is due to ionization of free enzyme. The kinetic behavior of bacterial sulfotransferase differed from that of mammalian phenol sulfotransferase.

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