PROSITE documentation PDOC60002

Phosphoketolase signatures

Phosphoketolases are key enzymes of the pentose phosphate pathway of heterofermentative and facultative homofermentative lactic acid bacteria and of the D-fructose 6-phosphate shunt of bifidobacteria. PK activity has been sporadically reported in other microorganisms including eukaryotic yeasts. Pks catalyze an irreversible thiamine diphosphate (ThDP) dependent phosphorolytic reaction splitting D-xylulose 5-phosphate (EC 4.1.2.9) or D-fructose 6-phosphate (EC 4.1.2.22) in the presence of inorganic phosphate to yield acetyl phosphate and glycerol 3-phosphate or erythrose 4-phosphate, respectively [1].

A multiple alignment of PK sequences shows several highly conserved regions. We selected two of these regions as signature patterns for PKs. The function of the first one is not known, whereas the second correspond to the ThDP binding site [1].