ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase
ADP-ribosyl cyclase homooctamer, Human
Identifiers
EC no.	3.2.2.6
CAS no.	9025-46-1
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / QuickGO
Search PMC articles PubMed articles NCBI proteins

In enzymology, a ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase (EC 3.2.2.6) is a bifunctional enzyme that catalyzes the chemical reaction

NAD⁺ + H₂O ${\displaystyle \rightleftharpoons }$ cADPR + H₂O + nicotinamide ${\displaystyle \rightleftharpoons }$ ADP-ribose + nicotinamide

The 3 substrates of this enzyme are NAD⁺ and H₂O, whereas its two products are ADP-ribose and nicotinamide. The reaction proceeds through cyclic ADP-ribose (cADPR) as intermediate, which is then hydrolyzed into ADP-ribose. This makes it different from NAD⁺ glycohydrolase (EC 3.2.2.5), where the reaction does not proceed through cADPR.^[1][2]

This enzyme belongs to the family of hydrolases, specifically those glycosylases that hydrolyse N-glycosyl compounds. Other names of this enzyme in common use include nicotinamide adenine dinucleotide (phosphate) nucleosidase, triphosphopyridine nucleotidase, NAD(P) nucleosidase, NAD(P)ase, and nicotinamide adenine dinucleotide (phosphate) glycohydrolase. This enzyme participates in nicotinate and nicotinamide metabolism.

• ALIVISATOS SG, WOOLLEY DW (1956). "Solubilization and purification of the diphosphopyridine nucleotidase from beef spleen". J. Biol. Chem. 219 (2): 823–32. PMID 13319302.
• ZATMAN LJ, KAPLAN NO, COLOWICK SP (1953). "Inhibition of spleen diphosphopyridine nucleotidase by nicotinamide, an exchange reaction". J. Biol. Chem. 200 (1): 197–212. PMID 13034774.
• Zatman LJ, Kaplan NO, Colowick SP, Ciotti MM (1953). "Formation of the isonicotinic acid hydrazide analog of DPN". J. Am. Chem. Soc. 75 (13): 3293–3294. doi:10.1021/ja01109a527.