TABLE 2.

Enzymes degrading dinucleoside polyphosphates.

Enzyme	Source/gene	Reactiona	References
“Symmetrical” Ap4A hydrolase	β- and γ-proteo bacteria (ApaH)	Ap4A → ADP + ADP	Guranowski et al., 1983; Guranowski, 2000
	Gram-positive bacteria (YqeK)	Ap4A → ADP + ADP	Minazzato et al., 2020
	Physarum polycephalum	Ap4A → ADP + ADP	Garrison et al., 1982
“Asymmetrical” Nudix Ap4A hydrolase	Animals (e.g., Nudt2), plants (e.g., AtNUDT25), proteobacteria (RppH/NudH/IalA/YgdP), mycobacteria (MutT1)	Ap4A → AMP + ATP	Guranowski, 2000; McLennan, 2006; Kraszewska, 2008; Arif et al., 2017
Ap4A phosphorylase	S. cerevisiae (Apa1, Apa2), protists, cyanobacteria, mycobacteria (MtApa)	Ap4A + Pi ↔ ADP + ATP	Guranowski and Blanquet, 1985; McLennan et al., 1994, 1996; Hou et al., 2013; Honda et al., 2015
HIT family hydrolases	S. cerevisiae (Aph), H. sapiens (FHIT)	Ap3A → AMP + ADP	Barnes et al., 1996
	Schizosaccharomyces pombe (Aph1)	Ap4A → AMP + ATP	Ingram and Barnes, 2000
Non-specific phosphodi esterases	H. sapiens (e.g., NPP1, NPP3, NPP4)	Ap4A → AMP + ATP	Guranowski, 2000

^aThe reaction with the best characterized or favored substrate is shown; other substrates may also be effective.