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 (Ap4A) hydrolases. PrpA exhibited a phosphatase activity towards p-nitrophenyl phosphate (pNPP), tyrosine phosphopeptide and tyrosine-phosphorylated protein, and a weak hydrolase activity towards ApnA and ATP. In the presence of Mn2+, PrpA hydrolyzed Ap4A into AMP and ATP, whereas in the presence of Co2+ PrpA hydrolyzed Ap4A into two molecules of ADP. ApaH exhibited high phosphatase activity towards pNPP, and hydrolase activity towards ApnA and ATP. Mn2+ was required for ApaH-mediated pNPP dephosphorylation and ATP hydrolysis, whereas Co2+ was required for ApnA hydrolysis. Thus, PrpA and ApaH may function mainly as a tyrosine protein phosphatase and an ApnA hydrolase, respectively.