S-adenosyl-L-homocysteine hydrolase
SMART accession number:SM00996
Description: -
Interpro abstract (IPR000043):

Adenosylhomocysteinase (S-adenosyl-L-homocysteine hydrolase, EC (AdoHcyase) is an enzyme of the activated methyl cycle, responsible for the reversible hydration of S-adenosyl-L-homocysteine into adenosine and homocysteine. This enzyme is ubiquitous, highly conserved, and may play a key role in the regulation of the intracellular concentration of adenosylhomocysteine. AdoHcyase requires NAD+ as a cofactor and contains a central glycine-rich region which is thought to be involved in NAD-binding. Since AdoHyc is a potent inhibitor of S-adenosyl-L-methionine dependent methyltransferases, AdoHycase plays a critical role in the modulation of the activity of various methyltransferases. The enzyme forms homotetramers, with each monomer binding one molecule of NAD+ [(PUBMED:9586999),(PUBMED:16061414),(PUBMED:11325033),(PUBMED:15165742)].

This family also includes S-adenosylhomocysteine hydrolase-like 1 (Ahcyl1), also known as IRBIT, and S-adenosylhomocysteine hydrolase-like protein 2 (Ahcyl2). Ahcyl1/IRBIT was shown to interact with inositol 1,4,5-trisphosphate receptors (IP3Rs), which function as intracellular Ca(2+) channels, and suppresses IP3 binding of IP3R [(PUBMED:16793548), (PUBMED:16527252)]. By competing with IP3, it modulates the threshold IP3 concentration required for the activation of the receptor [(PUBMED:16793548)]. Further studies indicate that Ahcyl1/IRBIT is in fact a multifunctional protein that regulates several ion channels and ion transporters [(PUBMED:24518248), (PUBMED:21152975)]. Despite its homology to S-adenosylhomocysteine hydrolases, Ahcyl1 has neither enzyme activity nor any effects on the enzyme activity of S-adenosylhomocysteine hydrolase [(PUBMED:12525476)]. Ahcyl2 lacks binding activity to IP3R [(PUBMED:19220705)]. Ahcyl2 upregulates NBCe1-B, which plays an important role in intracellular pH regulation [(PUBMED:27382360)].
Family alignment:
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There are 16360 AdoHcyase domains in 16358 proteins in SMART's nrdb database.

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