S-ribosylhomocysteine lyase

S-ribosylhomocysteine lyase
Identifiers
EC number	4.4.1.21
CAS number	37288-63-4
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 / EGO
Search PMC articles PubMed articles NCBI proteins

S-Ribosylhomocysteinase (LuxS)
crystal structure of autoinducer-2 production protein (luxs) from Haemophilus influenzae
Identifiers
Symbol	LuxS
Pfam	PF02664
Pfam clan	CL0094
InterPro	IPR003815
SCOP	1inn
SUPERFAMILY	1inn
Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

In enzymology, a S-ribosylhomocysteine lyase (EC 4.4.1.21) is an enzyme that catalyzes the chemical reaction

S-(5-deoxy-D-ribos-5-yl)-L-homocysteine $\rightleftharpoons$ L-homocysteine + (4S)-4,5-dihydroxypentan-2,3-dione

Hence, this enzyme has one substrate, S-(5-deoxy-D-ribos-5-yl)-L-homocysteine, and two products, L-homocysteine and (4S)-4,5-dihydroxypentan-2,3-dione.

This enzyme belongs to the family of lyases, specifically the class of carbon-sulfur lyases. The systematic name of this enzyme class is S-(5-deoxy-D-ribos-5-yl)-L-homocysteine L-homocysteine-lyase [(4S)-4,5-dihydroxypentan-2,3-dione-forming]. Other names in common use include S-ribosylhomocysteinase, and LuxS. This enzyme participates in methionine metabolism.

Furthermore, LuxS is involved in the synthesis of autoinducer AI-2 (autoinducer-2), which is plays a role in quorum sensing in a certain number of bacterial species. LuxS converts S-ribosylhomocysteine to homocysteine and 4,5-dihydroxy-2,3-pentanedione (DPD); DPD can then spontaneously cyclisize to active AI-2.^[1][2] AI-2 is a signalling molecule that is believe to act in interspecies communication by regulating niche-specific genes with diverse functions in various bacteria, often in response to population density. However, an unequivocally AI-2 related behavior was found to be restricted primarily to bacteria bearing known AI-2 receptor genes.^[3] Thus, while it is certainly true that some bacteria can respond to AI-2, it is doubtful that it is always being produced for purposes of signalling. LuxS is a homodimeric iron-dependent metalloenzyme containing two identical tetrahedral metal-binding sites similar to those found in peptidases and amidases.^[4]

Structural studies

As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes 1JQW, 2FQO, and 2FQT.

References

1. van Houdt R, Moons P, Jansen A, Vanoirbeek K, Michiels CW (September 2006). "Isolation and functional analysis of luxS in Serratia plymuthica RVH1". FEMS Microbiol. Lett. 262 (2): 201–9. doi:10.1111/j.1574-6968.2006.00391.x. PMID 16923076.
2. Zhu J, Patel R, Pei D (August 2004). "Catalytic mechanism of S-ribosylhomocysteinase (LuxS): stereochemical course and kinetic isotope effect of proton transfer reactions". Biochemistry 43 (31): 10166–72. doi:10.1021/bi0491088. PMID 15287744.
3. Rezzonico, F.; Duffy, B. (2008). "Lack of genomic evidence of AI-2 receptors suggests a non-quorum sensing role for LuxS in most bacteria". BMC Microbiology 8: 154. doi:10.1186/1471-2180-8-154. PMID 18803868.
4. Rajan R, Zhu J, Hu X, Pei D, Bell CE (March 2005). "Crystal structure of S-ribosylhomocysteinase (LuxS) in complex with a catalytic 2-ketone intermediate". Biochemistry 44 (10): 3745–53. doi:10.1021/bi0477384. PMID 15751951.

Further reading

• Zhu J, Dizin E, Hu X, Wavreille AS, Park J, Pei D (2003). "S-Ribosylhomocysteinase (LuxS) is a mononuclear iron protein". Biochemistry. 42 (16): 4717–26. doi:10.1021/bi034289j. PMID 12705835.
• Miller MB, Bassler BL (2001). "Quorum sensing in bacteria". Annu. Rev. Microbiol. 55: 165–99. doi:10.1146/annurev.micro.55.1.165. PMID 11544353.

This article incorporates text from the public domain Pfam and InterPro IPR003815