Photolabeling of dextransucrase from Streptococcus sanguis with p-azidophenyl α- d-glucopyranoside

Abstract

Dextransucrase from Streptococcus sanguis ATCC 10558 was photolabeled using p-azidophenyl α- d-glucopyranoside with an apparent rate constant of inactivation of 1.40 min −1. The dissociation constant for this compound, which acts as an acceptor molecule in the enzymatic reaction, is 90μ m. Apparently two acceptor binding sites exist on dextransucrase as shown by ( i.) photolabeling the enzyme with p-azidophenyl-α- d-[5,6- 3H]glucopyranoside and ( ii.) fluorescence titration experiments.