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2.4.1.370

Accepted name:

inositol phosphorylceramide mannosyltransferase

Reaction:

GDP-α-D-mannose + a (4R)-4-hydroxy-N-[(2R)-2-hydroxy-very-long-chain-acyl]-1-O-[(1D-myo-inositol-1-O-yl)hydroxyphosphoryl]sphinganine = a (4R)-4-hydroxy-N-[(2R)-2-hydroxy-very-long-chain-acyl]-1-O-{[6-O-(α-D-mannosyl)-1D-myo-inositol-1-O-yl]hydroxyphosphoryl}sphinganine + GDP

Glossary:

a (4R)-4-hydroxy-N-[(2R)-2-hydroxy-very-long-chain-acyl]-1-O-[(1D-myo-inositol-1-O-yl)hydroxyphosphoryl]sphinganine = a very-long-chain inositol phospho-α hydroxyphytoceramide = IPC
a (4R)-4-hydroxy-N-[(2R)-2-hydroxy-very-long-chain-acyl]-1-O-{[6-O-(α-D-mannosyl)-1D-myo-inositol-1-O-yl]hydroxyphosphoryl}sphinganine = a very-long-chain mannosylinositol phospho-α-hydroxyphytoceramide = MIPC

Other name(s):

SUR1 (gene name); CSH1 (gene name)

Systematic name:

GDP-α-D-mannose:(4R)-4-hydroxy-N-[(2R)-2-hydroxy-very-long-chain-acyl]-1-O-[(1D-myo-inositol-1-O-yl)hydroxyphosphoryl]sphinganine mannosyltransferase (configuration-retaining)

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. [DOI] [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. [DOI] [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. [DOI] [PMID: 12954640]

[EC 2.4.1.370 created 2019]

2.7.1.228

Accepted name:

mannosyl-inositol-phosphoceramide inositolphosphotransferase

Reaction:

1-phosphatidyl-1D-myo-inositol + a (4R)-4-hydroxy-N-[(2R)-2-hydroxy-very-long-chain-acyl]-1-O-{[6-O-(α-D-mannosyl)-1D-myo-inositol-1-O-yl]hydroxyphosphoryl}sphinganine = 1,2-diacyl-sn-glycerol + a (4R)-4-hydroxy-N-[(2R)-2-hydroxy-very-long-chain-acyl]-1-O-[(6-O-{6-O-[(1D-myo-inositol-1-O-yl)hydroxyphosphoryl]-α-D-mannosyl}-1D-myo-inositol-1-O-yl)hydroxyphosphoryl]sphinganine

Glossary:

a (4R)-4-hydroxy-N-[(2R)-2-hydroxy-very-long-chain-acyl]-1-O-{[6-O-(α-D-mannosyl)-1D-myo-inositol-1-O-yl]hydroxyphosphoryl}sphinganine = a very-long-chain mannosylinositol phospho-α-hydroxyphytoceramide = MIPC
a (4R)-4-hydroxy-N-[(2R)-2-hydroxy-very-long-chain-acyl]-1-O-[(6-O-{6-O-[(1D-myo-inositol-1-O-yl)hydroxyphosphoryl]-α-D-mannosyl}-1D-myo-inositol-1-O-yl)hydroxyphosphoryl]sphinganine = a very-long-chain mannosyl-diphosphoinositol-α-hydroxyphytoceramide = MIP2C

Other name(s):

IPT1 (gene name)

Systematic name:

1-phosphatidyl-1D-myo-inositol:(4R)-4-hydroxy-N-[(2R)-2-hydroxy-very-long-chain-acyl]-1-O-{[6-O-(α-D-mannosyl)-1D-myo-inositol-1-O-yl]hydroxyphosphoryl}sphinganine 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. [DOI] [PMID: 9368028]

[EC 2.7.1.228 created 2019]