KEGG   ENZYME: 3.2.1.140Help
Entry
EC 3.2.1.140                Enzyme                                 

Name
lacto-N-biosidase
Class
Hydrolases;
Glycosylases;
Glycosidases, i.e. enzymes that hydrolyse O- and S-glycosyl compounds
BRITE hierarchy
Sysname
oligosaccharide lacto-N-biosylhydrolase
Reaction(IUBMB)
beta-D-Gal-(1->3)-beta-D-GlcNAc-(1->3)-beta-D-Gal-(1->4)-D-Glc + H2O = beta-D-Gal-(1->3)-D-GlcNAc + beta-D-Gal-(1->4)-D-Glc [RN:R05166 R06116]
Reaction(KEGG)
Substrate
beta-D-Gal-(1->3)-beta-D-GlcNAc-(1->3)-beta-D-Gal-(1->4)-D-Glc [CPD:C06371];
H2O [CPD:C00001]
Product
beta-D-Gal-(1->3)-D-GlcNAc [CPD:C06372];
beta-D-Gal-(1->4)-D-Glc [CPD:C00243]
Comment
The enzyme from Streptomyces specifically hydrolyses the terminal lacto-N-biosyl residue (beta-D-Gal-(1->3)-D-GlcNAc) from the non-reducing end of oligosaccharides with the structure beta-D-Gal-(1->3)-beta-D-GlcNAc-(1->3)-beta-D-Gal-(1->R). Lacto-N-hexaose (beta-D-Gal-(1->3)-beta-D-GlcNAc-(1->3)-beta-D-Gal-(1->3)-beta-D-GlcNAc-(1->3)-beta-D-Gal-(1->4)-D-Glc) is hydrolysed to form first lacto-N-tetraose plus lacto-N-biose, with the subsequent formation of lactose. Oligosaccharides in which the non-reducing terminal Gal or the penultimate GlcNAc are replaced by fucose or sialic acid are not substrates. Asialo GM1 tetraose (beta-D-Gal-(1->3)-beta-D-GalNAc-(1->3)-beta-D-Gal-(1->4)-D-Glc) is hydrolysed very slowly, but lacto-N-neotetraose (beta-D-Gal-(1->4)-beta-D-GalNAc-(1->3)-beta-D-Gal-(1->4)-D-Glc) is not a substrate
History
EC 3.2.1.140 created 1999
Reference
1  [PMID:1528855]
  Authors
Sano M, Hayakawa K, Kato I.
  Title
An enzyme releasing lacto-N-biose from oligosaccharides.
  Journal
Proc. Natl. Acad. Sci. U. S. A. 89 (1992) 8512-6.
Reference
2  [PMID:7689556]
  Authors
Sano M, Hayakawa K, Kato I.
  Title
Purification and characterization of an enzyme releasing lacto-N-biose from oligosaccharides with type 1 chain.
  Journal
J. Biol. Chem. 268 (1993) 18560-6.
Other DBs
ExplorEnz - The Enzyme Database: 
IUBMB Enzyme Nomenclature: 
ExPASy - ENZYME nomenclature database: 
BRENDA, the Enzyme Database: 
CAS: 
146359-52-6

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