Enzymatic characteristics of an ApaH‐like phosphatase, PrpA, and a diadenosine tetraphosphate hydrolase, ApaH, from Myxococcus xanthus

We characterized the activities of the Myxococcus xanthus ApaH‐like phosphatases PrpA and ApaH, which share homologies with both phosphoprotein phosphatases and diadenosine tetraphosphate (Ap 4 A) hydrolases. PrpA exhibited a phosphatase activity towards p ‐nitrophenyl phosphate ( p NPP), tyrosine phosphopeptide and tyrosine‐phosphorylated protein, and a weak hydrolase activity towards Ap n A and ATP. In the presence of Mn 2+ , PrpA hydrolyzed Ap 4 A into AMP and ATP, whereas in the presence of Co 2+ PrpA hydrolyzed Ap 4 A into two molecules of ADP. ApaH exhibited high phosphatase activity towards p NPP, and hydrolase activity towards Ap n A and ATP. Mn 2+ was required for ApaH‐mediated p NPP dephosphorylation and ATP hydrolysis, whereas Co 2+ was required for Ap n A hydrolysis. Thus, PrpA and ApaH may function mainly as a tyrosine protein phosphatase and an Ap n A hydrolase, respectively.