S-adenosyl-L-homocysteine hydrolase () (AdoHcyase) is an
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
of the activated methyl cycle, responsible for the reversible hydration of
S-adenosyl-L-homocysteine into
adenosine
Adenosine ( symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. Adenosine is one of the four nucleoside building ...
and
homocysteine.
AdoHcyase is a ubiquitous enzyme which binds and requires
NAD+ as a cofactor. AdoHcyase is a highly conserved protein
of about 430 to 470 amino acids. The family contains a
glycine-rich region in the central part of AdoHcyase; a region thought to be involved in NAD-binding.
AdoHcyase is significantly associated with adenosine deaminase deficiency, which classically manifests in severe combine immunodeficiency (SCID). Accumulated adenosine derivatives, dATPs, irreversibly bind to and inhibit AdoHcyase, promoting the buildup of S-adenosyl-L-homocystine (due to equilibrium constant favors S-adenosyl-L-homocystine), a potent inhibitor of methyl transfer reactions.
This protein may use the
morpheein
Morpheeins are proteins that can form two or more different homo-oligomers (morpheein forms), but must come apart and change shape to convert between forms. The alternate shape may reassemble to a different oligomer. The shape of the subunit ...
model of
allosteric regulation
In biochemistry, allosteric regulation (or allosteric control) is the regulation of an enzyme by binding an effector molecule at a site other than the enzyme's active site.
The site to which the effector binds is termed the ''allosteric site ...
.
References
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