Table 1 –
Major enzymes of adenosine metabolism
| Enzyme or enzyme family | EC number | Isozyme | Gene name | Alternative names and aliases | Catalytic reaction | Compartmentalization |
|---|---|---|---|---|---|---|
| Ecto-nucleoside triphosphate diphosphohydrolase (NTPDase) family | 3.6.1.5 | NTPDase1 NTPDase2 NTPDase3 NTPDase8 |
ENTPD1 ENTPD2 ENTPD3 ENTPD8 |
CD39, apyrase, ecto-ATPase, ATP-diphosphohydrolase | ATP + H20 → ADP + Pi ADP + H20 → AMP + Pi |
extracellular, microvesicles, soluble |
| Ecto-nucleotide pyrophosphatase/phosphodiesterase (NPP) family | 3.6.1.9 3.1.4.1 |
NPP1 NPP3 |
ENPP1 ENPP3 |
PC-1, CD203a Phosphodiesterase-1β, CD203c, gp130RB13–6, B10 | ATP + H20 → AMP + PPi ADPR → AMP + PPi Ap4A → ATP + AMP |
extracellular, soluble |
| Ecto-5′-nucleotidase (eN) | 3.1.3.5 | NT5E | CD73 | AMP + H20 → Adenosine + Pi | extracellular, microvesicles, soluble | |
| Alkaline phosphatase (ALP) family | 3.1.3.1 | TNAP | ALPL | Tissue-nonspecific alkaline phosphatase (TNAP) | ATP + 3H20 → Adenosine + 3Pi PPi → 2Pi |
extracellular, microvesicles, soluble |
| CD38 | 3.2.2.5 3.2.2.6 |
CD38 | NAD+ glycohydrolase, NAD nucleosidase, NADase, Cyclic ADP-ribose hydrolase, | NAD+ + H20 → ADPR + nicotinamide cyclic ADP-ribose + H2O → ADPR-D-ribose | extracellular, intracellular, soluble | |
| CD157 | 2.4.99.20 | BST1 | Cyclic ADP-ribosyl cyclase 2, ADP-ribosyltransferase | cyclic ADP-ribose + H2O → ADPR-D-ribose | extracellular | |
| Adenylate kinase (AK) | 2.7.4.10 | AK1 | AK1 | Myokinase | ATP + AMP ↔ 2ADP | extracellular, intracellular, soluble |
| Nucleoside diphosphate kinase (NDPK) | 2.7.4.6 | NDPK-A NDPK-B |
NME1 NME2 |
Nm23-H1, NME1, Nm23-H2, NME2 | ATP + NDP ↔ ADP + NTP | extracellular, intracellular, soluble |
| Adenosine deaminase (ADA) family | 3.1.3.1 | ADA1 ADA2 |
ADA1 ADA2 |
Adenosine + H20 → Inosine | extracellular, intracellular, soluble | |
| Purine nucleoside phosphorylase (PNP) | 2.4.2.2 | PNP | Inosine phosphorylase | Inosine + Pi ↔ hypoxanthine + alpha-D-ribose 1-phosphate | extracellular, intracellular | |
| Adenosine kinase (ADK) | 2.7.1.20 | ADK-S ADK-L |
ADK | Adenosine + ATP → AMP + ADP | intracellular intranuclear |
This table highlights the converting pathways for adenine nucleotides and adenosine. However, additional nucleotides and related compounds also serve as preferred substrates for these (ecto)enzymes.