Information on EC 2.4.1.260 - dolichyl-P-Man:Man7GlcNAc2-PP-dolichol alpha-1,6-mannosyltransferase

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The enzyme appears in viruses and cellular organisms

EC NUMBER
COMMENTARY hide
2.4.1.260
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RECOMMENDED NAME
GeneOntology No.
dolichyl-P-Man:Man7GlcNAc2-PP-dolichol alpha-1,6-mannosyltransferase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
dolichyl beta-D-mannosyl phosphate + D-Man-alpha-(1->2)-D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-[D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-D-Man-alpha-(1->6)]-D-Man-beta-(1->4)-D-GlcNAc-beta-(1->4)-D-GlcNAc-diphosphodolichol = D-Man-alpha-(1->2)-D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-[D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-[D-Man-alpha-(1->6)]-D-Man-alpha-(1->6)]-D-Man-beta-(1->4)-D-GlcNAc-beta-(1->4)-D-GlcNAc-diphosphodolichol + dolichyl phosphate
show the reaction diagram
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
protein N-glycosylation (eukaryotic, high mannose)
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dolichyl-diphosphooligosaccharide biosynthesis
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N-Glycan biosynthesis
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Various types of N-glycan biosynthesis
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Metabolic pathways
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SYSTEMATIC NAME
IUBMB Comments
dolichyl beta-D-mannosyl phosphate:D-Man-alpha-(1->2)-D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-[D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-D-Man-alpha-(1->6)]-D-Man-beta-(1->4)-D-GlcNAc-beta-(1->4)-D-GlcNAc-diphosphodolichol alpha-1,6-mannosyltransferase
The formation of N-glycosidic linkages of glycoproteins involves the ordered assembly of the common Glc3Man9GlcNAc2 core-oligosaccharide on the lipid carrier dolichyl diphosphate. Early mannosylation steps occur on the cytoplasmic side of the endoplasmic reticulum with GDP-Man as donor, the final reactions from Man5GlcNAc2-PP-Dol to Man9Glc-NAc2-PP-Dol on the lumenal side use dolichyl beta-D-mannosyl phosphate.
ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
; gene ALG12
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Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
malfunction
physiological function
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
dolichyl beta-D-mannosyl phosphate + D-Man-alpha-(1->2)-D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-[D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-D-Man-alpha-(1->6)]-D-Man-beta-(1->4)-D-GlcNAc-beta-(1->4)-D-GlcNAc-diphosphodolichol
D-Man-alpha-(1->2)-D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-[D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-[D-Man-alpha-(1->6)]-D-Man-alpha-(1->6)]-D-Man-beta-(1->4)-D-GlcNAc-beta-(1->4)-D-GlcNAc-diphosphodolichol + dolichyl phosphate
show the reaction diagram
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
dolichyl beta-D-mannosyl phosphate + D-Man-alpha-(1->2)-D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-[D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-D-Man-alpha-(1->6)]-D-Man-beta-(1->4)-D-GlcNAc-beta-(1->4)-D-GlcNAc-diphosphodolichol
D-Man-alpha-(1->2)-D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-[D-Man-alpha-(1->2)-D-Man-alpha-(1->3)-[D-Man-alpha-(1->6)]-D-Man-alpha-(1->6)]-D-Man-beta-(1->4)-D-GlcNAc-beta-(1->4)-D-GlcNAc-diphosphodolichol + dolichyl phosphate
show the reaction diagram
P53730
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SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
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primary fibroblasts obtained from skin biopsies
Manually annotated by BRENDA team
Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
expression of the human ALG12 cDNA under the control of the GPD promoter in Dalg12wbp1–2 yeasts. Growth of Dalg12wbp1–2 yeasts is restored by expression of this cDNA, thus establishing the function of the corresponding protein. The two mutant ALG12 alleles found in the congenital disorder of glycosylation patient, namely ALG12[T67M] and ALG12[R146Q], do very weakly restore growth to the levels reached with the normal human ALG12 cDNA
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
E38K
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the wild-type EBS4 gene but not the mutated EBS4 plasmid carrying the E38K mutation (ebs4-3) is able to complement the yeast DELTAalg12 mutation
R100W
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residue R100 is located near the end of the largest luminal loop between the first two predicted transmembrane segments and is absolutely conserved in all known ALG9 enzymes. Mutation suppresses a dwarf mutant, bri1-9, the phenotypes of which are caused by endoplasmic reticulum retention and endoplasmic reticulum-associated degradation of a brassinosteroid receptor, BRASSINOSTEROID-INSENSITIVE 1, BR1. The mutation prevents the Glc3Man9GlcNAc2 assembly and inhibits the endoplasmic reticulum-associated degradation of bri1-9. Overexpression of EBS4 in the R100W bri1-9 mutant, which encodes the Arabidopsis ortholog of the yeast ALG12 catalyzing the ER luminal alpha1,6 Man addition, adds an alpha1,6 Man to the truncated N-glycan precursor accumulated in R100W bri1-9, promotes the bri1-9 endoplasmic reticulum-associated degradation, and neutralizes the R100W suppressor phenotype
F142V
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the F142V replacement in hALG12p is the cause of inefficient addition of the eighth mannose residue onto Man7GlcNAc2-PP-dolichol during glycoprotein biosynthesis in a patient with type I congenital disorders of glycosylation. The patient is homozygous for the point mutation that causes an amino acid substitution in a conserved region of dolichyl-P-Man:Man7GlcNAc2-PP-dolichyl alpha6-mannosyltransferase. Skin biopsy fibroblasts from a CDG I patient have a reduced capacity to add the eighth mannose residue onto the lipid-linked oligosaccharide precursor. The fibroblasts of the patient are capable of the direct transfer of Man7GlcNAc2 from dolichol onto protein and that this N-linked structure can be glucosylated by UDP-glucose:glycoprotein glucosyltransferase in the endoplasmic reticulum
R146Q
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congenital disorder of glycosylation type lg is identified in a child presenting with psychomotor retardation, hypotonia, growth retardation, dysmorphic features and anorexia. In the patient’s fibroblasts, the biosynthetic intermediate GlcNAc2Man7 oligosaccharide is detected both on the lipid carrier dolichyl pyrophosphate and on newly synthesized glycoproteins, pointing to a defect in the dolichyl pyrophosphate–GlcNAc2Man7-dependent ALG12 alpha1,6 mannosyltransferase. Analysis of the ALG12 cDNA in the CDG patient revealed compound heterozygosity for two point mutations that result in the amino acid substitutions T67M and R146Q, respectively. The impact of these mutations on ALG12 protein function is investigated in the Saccharomyces cerevisiae alg12 glycosylation mutant by showing that the yeast ALG12 gene bearing the homologous mutations T61M and R161Q and the human mutant ALG12 cDNA alleles fail to normalize the growth defect phenotype of the alg12 yeast model, whereas expression of the normal ALG12 cDNA complements the yeast mutation. The ALG12 mannosyltransferase defect defines a type of congenital disorder of glycosylation, designated CDG-Ig
T67M
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congenital disorder of glycosylation type lg is identified in a child presenting with psychomotor retardation, hypotonia, growth retardation, dysmorphic features and anorexia. In the patient’s fibroblasts, the biosynthetic intermediate GlcNAc2Man7 oligosaccharide is detected both on the lipid carrier dolichyl pyrophosphate and on newly synthesized glycoproteins, pointing to a defect in the dolichyl pyrophosphate–GlcNAc2Man7-dependent ALG12 alpha1,6 mannosyltransferase. Analysis of the ALG12 cDNA in the CDG patient revealed compound heterozygosity for two point mutations that result in the amino acid substitutions T67M and R146Q, respectively. The impact of these mutations on ALG12 protein function is investigated in the Saccharomyces cerevisiae alg12 glycosylation mutant by showing that the yeast ALG12 gene bearing the homologous mutations T61M and R161Q and the human mutant ALG12 cDNA alleles fail to normalize the growth defect phenotype of the alg12 yeast model, whereas expression of the normal ALG12 cDNA complements the yeast mutation. The ALG12 mannosyltransferase defect defines a type of congenital disorder of glycosylation, designated CDG-Ig