The Enzyme Database

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EC 2.4.1.370     
Accepted name: inositol phosphorylceramide mannosyltransferase
Reaction: GDP-α-D-mannose + a very-long-chain inositol phospho-(2′R)-2′-hydroxyphytoceramide = a very-long-chain mannosylinositol phospho-(2′R)-2′-hydroxyphytoceramide + GDP
Glossary: a very-long-chain mannosylinositol phospho-(2′R)-2′-hydroxyphytoceramide = a very-long-chain mannosylinositol phospho-α-hydroxyphytoceramide = MIPC
Other name(s): SUR1 (gene name); CSH1 (gene name)
Systematic name: GDP-α-D-mannose:inositol phospho-(2′R)-2′-hydroxyphytoceramide mannosyltransferase
Comments: The simplest complex sphingolipid of yeast, inositol-phospho-α-hydroxyphytoceramide (IPC), is usually mannosylated to yield mannosyl-inositol-phospho-α hydroxyphytoceramide (MIPC). The enzyme is located in the Golgi apparatus, and utilizes GDP-mannose as the mannosyl group donor. It consists of a catalytic subunit (SUR1 or CSH1) and a regulatory subunit (CSG2).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Beeler, T.J., Fu, D., Rivera, J., Monaghan, E., Gable, K. and Dunn, T.M. SUR1 (CSG1/BCL21), a gene necessary for growth of Saccharomyces cerevisiae in the presence of high Ca2+ concentrations at 37 degrees C, is required for mannosylation of inositolphosphorylceramide. Mol. Gen. Genet. 255 (1997) 570–579. [PMID: 9323360]
2.  Dean, N., Zhang, Y.B. and Poster, J.B. The VRG4 gene is required for GDP-mannose transport into the lumen of the Golgi in the yeast, Saccharomyces cerevisiae. J. Biol. Chem. 272 (1997) 31908–31914. [PMID: 9395539]
3.  Uemura, S., Kihara, A., Inokuchi, J. and Igarashi, Y. Csg1p and newly identified Csh1p function in mannosylinositol phosphorylceramide synthesis by interacting with Csg2p. J. Biol. Chem. 278 (2003) 45049–45055. [PMID: 12954640]
[EC 2.4.1.370 created 2019]
 
 
EC 2.7.1.228     
Accepted name: mannosyl-inositol-phosphoceramide inositolphosphotransferase
Reaction: 1-phosphatidyl-1D-myo-inositol + a very-long-chain mannosylinositol phospho-(2′R)-2′-hydroxyphytoceramide = 1,2-diacyl-sn-glycerol + a very-long-chain mannosyl-diphosphoinositol-(2′R)-2′-hydroxyphytoceramide
Glossary: a very-long-chain mannosyl-diphosphoinositol-(2′R)-2′-hydroxyphytoceramide = a very-long-chain mannosyl-diphosphoinositol-α-hydroxyphytoceramide = MIP2C
Other name(s): IPT1 (gene name)
Systematic name: 1-phosphatidyl-1D-myo-inositol:mannosylinositol phospho-(2′R)-2′-hydroxyphytoceramide phosphoinositoltransferase
Comments: This enzyme catalyses the ultimate reaction in the yeast sphingolipid biosynthesis pathway. It transfers a second phosphoinositol group to mannosyl-inositol-phospho-α-hydroxyphytoceramide (MIPC), forming the final and most abundant yeast sphingolipid, mannosyl-diphosphoinositol-ceramide (MIP2C).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Dickson, R.C., Nagiec, E.E., Wells, G.B., Nagiec, M.M. and Lester, R.L. Synthesis of mannose-(inositol-P)2-ceramide, the major sphingolipid in Saccharomyces cerevisiae, requires the IPT1 (YDR072c) gene. J. Biol. Chem. 272 (1997) 29620–29625. [PMID: 9368028]
[EC 2.7.1.228 created 2019]
 
 


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