GO:0004081:   bis(5"-nucleosyl)-tetraphosphatase (asymmetrical) activity
Catalysis of the reaction: P(1),P(4)-bis(5"-nucleosyl)tetraphosphate + H2O = NTP + NMP. Acts on bis(5"-guanosyl)-, bis(5"-xanthosyl)-, bis(5"-adenosyl)- and bis(5"-uridyl)-tetraphosphate.