Helicobacter pylori 3-deoxy-D-manno-octulosonate-8-phosphate (KDO-8-P) synthase is a zinc-metalloenzyme.

摘要: Abstract 3-Deoxy- D - manno -2-octulosonate-8-phosphate (KDO-8-P) synthase catalyzes the aldol-type condensation of phosphoenolpyruvate and -arabinose-5-phosphate (A-5-P) to produce KDO-8-P inorganic phosphate. All synthases, as exemplified by enzyme from Escherichia coli , were believed not require a metal cofactor for catalytic activity. However, recent studies have demonstrated that Aquifex aeolicus is metalloenzyme. Moreover, sequence alignments phylogenetic analysis protein sequences strongly suggested there whole subfamily synthases are also metalloenzymes. One these putative metalloenzymes ortholog human pathogen Helicobacter pylori . In order test this model, we cloned kdsa gene encoding H. synthase, overexpressed purified protein. This was found bind one mol Zn/mol monomer, removal treatment with 2,6-pyridine dicarboxylic acid abolished enzymatic The Zn 2+ in could be quantitatively replaced Cd which increased observed k cat ∼2-fold, decreased apparent K m ∼6.5-fold. Furthermore, did greatly perturb its circular dichroism spectra. Thus, divalent most likely serves directly involved catalysis.