Adenosylhomocysteinase

S-Adenosylhomocysteine hydrolase
SAH hydrolase tetramer, Human
Identifiers
Symbol	AHCY
NCBI gene	191
HGNC	343
OMIM	180960
RefSeq	NM_000687
UniProt	P23526
Other data
EC number	3.3.1.1
Locus	Chr. 20 q11.22

Adenosylhomocysteinase (EC 3.3.1.1, S-adenosylhomocysteine synthase, S-adenosylhomocysteine hydrolase, adenosylhomocysteine hydrolase, S-adenosylhomocysteinase, SAHase, AdoHcyase) is an enzyme that converts S-adenosylhomocysteine to homocysteine and adenosine.^[1]^[2] This enzyme catalyses the following chemical reaction

The enzyme contains one tightly bound NAD⁺ per subunit.

References[edit]

^ De La Haba G, Cantoni GL (March 1959). "The enzymatic synthesis of S-adenosyl-L-homocysteine from adenosine and homocysteine". The Journal of Biological Chemistry. 234 (3): 603–8. PMID 13641268.
^ Palmer JL, Abeles RH (February 1979). "The mechanism of action of S-adenosylhomocysteinase". The Journal of Biological Chemistry. 254 (4): 1217–26. PMID 762125.

Adenosylhomocysteinase at the US National Library of Medicine Medical Subject Headings (MeSH)

Essential amino acids are in Capitals

LYSINE→	Saccharopine dehydrogenase Glutaryl-CoA dehydrogenase
LEUCINE→	3-Hydroxybutyryl-CoA dehydrogenase Branched-chain amino acid aminotransferase Branched-chain alpha-keto acid dehydrogenase complex Enoyl-CoA hydratase HMG-CoA lyase HMG-CoA reductase Isovaleryl coenzyme A dehydrogenase α-Ketoisocaproate dioxygenase Leucine 2,3-aminomutase Methylcrotonyl-CoA carboxylase Methylglutaconyl-CoA hydratase (See Template:Leucine metabolism in humans – this diagram does not include the pathway for β-leucine synthesis via leucine 2,3-aminomutase)
TRYPTOPHAN→	Indoleamine 2,3-dioxygenase/Tryptophan 2,3-dioxygenase Arylformamidase Kynureninase 3-hydroxyanthranilate oxidase Aminocarboxymuconate-semialdehyde decarboxylase Aminomuconate-semialdehyde dehydrogenase
PHENYLALANINE→tyrosine→	(see below)

glycine→serine→	Serine hydroxymethyltransferase Serine dehydratase glycine→creatine: Guanidinoacetate N-methyltransferase Creatine kinase
alanine→	Alanine transaminase
cysteine→	D-cysteine desulfhydrase
threonine→	L-threonine dehydrogenase

HISTIDINE→	Histidine ammonia-lyase Urocanate hydratase Formiminotransferase cyclodeaminase
proline→	Proline oxidase Pyrroline-5-carboxylate reductase 1-Pyrroline-5-carboxylate dehydrogenase/ALDH4A1 PYCR1
arginine→	Ornithine aminotransferase Ornithine decarboxylase Agmatinase
→alpha-ketoglutarate→TCA	Glutamate dehydrogenase
Other	cysteine+glutamate→glutathione: Gamma-glutamylcysteine synthetase Glutathione synthetase Gamma-glutamyl transpeptidase glutamate→glutamine: Glutamine synthetase Glutaminase

VALINE→	Branched-chain amino acid aminotransferase Branched-chain alpha-keto acid dehydrogenase complex Enoyl-CoA hydratase 3-hydroxyisobutyryl-CoA hydrolase 3-hydroxyisobutyrate dehydrogenase Methylmalonate semialdehyde dehydrogenase
ISOLEUCINE→	Branched-chain amino acid aminotransferase Branched-chain alpha-keto acid dehydrogenase complex 3-hydroxy-2-methylbutyryl-CoA dehydrogenase
METHIONINE→	generation of homocysteine: Methionine adenosyltransferase Adenosylhomocysteinase regeneration of methionine: Methionine synthase/Homocysteine methyltransferase Betaine-homocysteine methyltransferase conversion to cysteine: Cystathionine beta synthase Cystathionine gamma-lyase
THREONINE→	Threonine aldolase
→succinyl-CoA→TCA	Propionyl-CoA carboxylase Methylmalonyl CoA epimerase Methylmalonyl-CoA mutase

PHENYLALANINE→tyrosine→	Phenylalanine hydroxylase Tyrosine aminotransferase 4-Hydroxyphenylpyruvate dioxygenase Homogentisate 1,2-dioxygenase Fumarylacetoacetate hydrolase tyrosine→melanin: Tyrosinase

asparagine→aspartate→	Asparaginase/Asparagine synthetase Aspartate transaminase

v t e Enzymes
Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Catalytically perfect enzyme Coenzyme Cofactor Enzyme catalysis
Regulation	Allosteric regulation Cooperativity Enzyme inhibitor Enzyme activator
Classification	EC number Enzyme superfamily Enzyme family List of enzymes
Kinetics	Enzyme kinetics Eadie–Hofstee diagram Hanes–Woolf plot Lineweaver–Burk plot Michaelis–Menten kinetics
Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list) EC7 Translocases (list)

v t e Hydrolases: ether bond (EC 3.3)
3.3.1	Adenosylhomocysteinase
3.3.2	Epoxide hydrolase Leukotriene-A4 hydrolase