alliin lyase | |||||||||
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Identifiers | |||||||||
EC no. | 4.4.1.4 | ||||||||
CAS no. | 9031-77-0 | ||||||||
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 | ||||||||
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Alliinase_C | |||||||||
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![]() Crystal structure of alliinase from garlic- apo form | |||||||||
Identifiers | |||||||||
Symbol | Alliinase_C | ||||||||
Pfam | PF04864 | ||||||||
Pfam clan | CL0061 | ||||||||
InterPro | IPR006948 | ||||||||
SCOP2 | 1lk9 / SCOPe / SUPFAM | ||||||||
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Alliinase EGF-like domain | |||||||||
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![]() Crystal structure of alliinase from garlic- apo form | |||||||||
Identifiers | |||||||||
Symbol | EGF_alliinase | ||||||||
Pfam | PF04863 | ||||||||
Pfam clan | CL0001 | ||||||||
InterPro | IPR006947 | ||||||||
SCOP2 | 1lk9 / SCOPe / SUPFAM | ||||||||
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In enzymology, an alliin lyase (EC 4.4.1.4) is an enzyme that catalyzes the chemical reaction
Hence, this enzyme has one substrate, S-alkyl-L-cysteine S-oxide, and two products, alkyl sulfenate and 2-aminoacrylate.
This enzyme belongs to the family of lyases, specifically the class of carbon-sulfur lyases. The systematic name of this enzyme class is S-alkyl-L-cysteine S-oxide alkyl-sulfenate-lyase (2-aminoacrylate-forming). Other names in common use include alliinase, cysteine sulfoxide lyase, alkylcysteine sulfoxide lyase, S-alkylcysteine sulfoxide lyase, L-cysteine sulfoxide lyase, S-alkyl-L-cysteine sulfoxide lyase, and alliin alkyl-sulfenate-lyase. It employs one cofactor, pyridoxal phosphate.
Many alliinases contain a novel N-terminal epidermal growth factor-like domain (EGF-like domain). [1]
These enzymes are found in plants of the genus Allium , such as garlic and onions. Alliinase is responsible for catalyzing chemical reactions that produce the volatile chemicals that give these foods their flavors, odors, and tear-inducing properties. Alliinases are part of the plant's defense against herbivores. Alliinase is normally sequestered within a plant cell, but, when the plant is damaged by a feeding animal, the alliinase is released to catalyze the production of the pungent chemicals. This tends to have a deterrent effect on the animal. The same reaction occurs when onion or garlic is cut with a knife in the kitchen.
In garlic, an alliinase enzyme acts on the chemical alliin converting it into allicin. The process involves two stages: elimination of 2-propenesulfenic acid from the amino acid unit (with dehydroalanine as a byproduct), and then condensation of two of the sulfenic acid molecules.
Alliin and related substrates found in nature are chiral at the sulfoxide position (usually having the S absolute configuration, and alliin itself was the first natural product found to have both carbon- and sulfur-centered stereochemistry. [2] However, the sulfenic acid intermediate is not chiral, and the final product's stereochemistry is not controlled.
There are a range of similar enzymes that can react with the cysteine-derived sulfoxides present in different species. In onions, an isomer of alliin, isoalliin, is converted to 1-propenesulfenic acid. A separate enzyme, the lachrymatory factor synthase or LFS, then converts this chemical to syn-propanethial-S-oxide, a potent lachrymator. The analogous butyl compound, syn-butanethial-S-oxide, is found in Allium siculum species. [3]
As of late 2007, three structures have been solved for this class of enzymes, using X-ray crystallography. The PDB accession codes are 1LK9, 2HOR, and 2HOX.