phosphatidylinositol [PI] synthase; CDP diacylglycerol inositol-3-phosphatidyltransferase (CDIPT, PIS1)

Function

• catalyzes biosynthesis of phosphatidylinositol (Ptdins) & Ptdins:inositol exchange reaction
• may act to diminish excessive cellular Ptdins
• exchange activity is due to the reverse reaction of Ptdins synthase & is dependent on CMP, which is tightly bound to the enzyme

Inhibition:

• inhibited by Ptdins (product inhibition), phosphatidylinositol phosphate, & nucleoside di- & tri-phosphates

CDP-diacylglycerol + myo-inositol
                 <-->
CMP + phosphatidyl-1D-myo-inositol

Cofactor: Mg+2, Mn+2

Kinetic parameters:

• Optimum pH is 9.0
• Optimum temperature is 50 degrees celsius

Structure

• belongs to the CDP-alcohol phosphatidyltransferase class-I family

Compartment

• endoplasmic reticulum membrane, Golgi membrane

Alternative splicing

named isoforms=2

Expression

• widely expressed
• expressed in adult liver & skeletal muscle > pancreas, kidney, lung, placenta, brain, heart, leukocyte, colon, small intestine, ovary, testis, prostate, thymus & spleen
• in fetus, expressed in kidney, liver, lung & brain

More general terms

• phosphotransferase
• transmembrane 5 protein

Database

• OMIM: https://mirror.omim.org/entry/605893
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:1042
• UniProt: http://www.uniprot.org/uniprot/O14735.html