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Pathway: phosphatidylinositol biosynthesis

Biochemical pathways in S. cerevisiae are manually curated and maintained in the YeastPathways database. This page summarizes the genes, enzymes, and metabolites involved in the pathway, along with the curated literature.

Pathway Name
phosphatidylinositol biosynthesis
Pathway ID
PWY3O-3
SGD ID
SGD:S000203378
Genes
PIS1
Aliases
PI biosynthesis
Chemical Compounds
1-phosphatidyl-1D-myo-inositol(1-) | cytidine 5'-monophosphate(2-) | hydron | myo-inositol

Pathway Diagram

Diagram of the pathway from YeastPathways. Click "View interactive diagram at YeastPathways" for the zoomable, clickable version.

phosphatidylinositol biosynthesis pathway diagram

View interactive diagram at YeastPathways

Pathway Summary

Phosphatidylinositol (PI) is an essential myo-inositol-containing phospholipid in all eukaryotes. It is the third most abundant phospholipid found in the membranes of S. cerevisiae and a precursor to phosphoinositides, inositol polyphosphates, and complex sphingolipids. PI and its metabolites are involved in a variety of biological processes including signal transduction, nuclear mRNA export, vesicle trafficking, and synthesis of the lipid anchor glycosylphosphatidylinositol. PI is synthesized at the endoplasmic reticulum from cytidine diphosphate diacylglycerol (CDP-DAG) and inositol in a reaction catalyzed by PI synthase (Pis1p). Synthesis of PI is increased by exogenously supplied inositol or zinc depletion. When cells are grown in inositol, PI synthase activity is greatly stimulated while phosphatidylserine synthase (Cho1p), which competes with Pis1p for their common substrate, CDP-DAG, is inhibited. Under conditions of zinc depletion, the transcription factor Zap1p binds to a zinc-responsive cis-acting element (UAS-ZRE) in the PIS1 promoter and increases PI synthase expression. Increased PI synthesis through zinc depletion or inositol supplementation leads to reduced CDP-DAG levels as well as its precursor, phosphatidic acid (PA). This PA level drop causes the Opi1p repressor to translocate to the nucleus, where it subsequently represses the transcription of many UAS-INO-containing phospholipid biosynthetic genes. Thus, in addition to its role in the biosynthesis of many important metabolites, PI synthesis indirectly contributes to the transcriptional regulation of phospholipid metabolism through its effect on intracellular PA level.

Genes Involved

Genes whose products participate in this pathway, with their systematic names, EC numbers (where the gene product is an enzyme with an assigned EC number), and the gene's SGD description.

GeneSystematic NameEC NumberDescription
PIS1 YPR113W 2.7.8.11 Phosphatidylinositol synthase

Functional Networks

Functional Networks show how the genes in this pathway work together: a graph linking the pathway to its genes and their shared GO biological-process terms and phenotype observables, and the GO-CAM causal activity models that involve these genes.

Shared Annotations

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GO-CAMs

GO-CAM (Gene Ontology Causal Activity Model) pathway models that involve the genes in this pathway. A gene can participate in more than one model, so use the dropdown to switch between them; the model for this pathway is shown by default.

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GO Enrichment

Gene Ontology biological-process terms enriched among the genes in this pathway, computed with GO Term Finder. Terms are shown with the number of pathway genes annotated to them and the corrected p-value.

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References

List of references used specifically to curate the information on this page.

Resources

YeastPathways