Chemical modification of dextransucrase from Leuconostoc mesenteroides NRRL B-512F by pyridoxal 5'-phosphate: evidence for the presence of an essential lysine residue at the active site.

The treatment of Leuconostoc mesenteroides NRRL B-512F dextransucrase with lysine specific reagent, pyridoxal 5'-phosphate (PLP) at pH 5.2 and 30 degrees C resulted in the loss of enzyme activity. The inactivation by PLP could be reversed completely by dilution or dialysis. Sucrose as well as acceptor substrates, glucose and dextran protected the enzyme against inactivation by PLP. A statistical, kinetic analysis of the inactivation by PLP showed that one lysine residue is essential for the enzyme activity. All these results showed that one lysine residue present at the active is essential for the activity of dextransucrase.