Phosphatidylinositol 3-phosphate (PtdIns3''P'') is a

phospholipid Phospholipids, are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...

found in

cell membranes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...

that helps to recruit a range of proteins, many of which are involved in protein trafficking, to the membranes. It is the product of both the class II and III

phosphoinositide 3-kinases Phosphoinositide 3-kinases (PI3Ks), also called phosphatidylinositol 3-kinases, are a family of enzymes involved in cellular functions such as cell growth, proliferation, differentiation, motility, survival and intracellular trafficking, which i ...

(PI 3-kinases) activity on

phosphatidylinositol Phosphatidylinositol (or Inositol Phospholipid) consists of a family of lipids as illustrated on the right, where red is x, blue is y, and black is z, in the context of independent variation, a class of the phosphatidylglycerides. In such molecul ...

. PtdIns3''P'' is dephosphorylated by the myotubularin family of

phosphatase In biochemistry, a phosphatase is an enzyme that uses water to cleave a phosphoric acid Ester, monoester into a phosphate ion and an Alcohol (chemistry), alcohol. Because a phosphatase enzyme catalysis, catalyzes the hydrolysis of its Substrate ...

s, on the D3 position of the inositol ring, and can be converted to PtdIns(3,5)''P''₂ by the lipid kinase PIKfyve. Both FYVE domains and

PX domain The PX domain is a phosphoinositide-binding structural domain involved in targeting of proteins to cell membranes. This domain was first found in P40phox and p47phox domains of NADPH oxidase (phox stands for phagocytic oxidase). It was also ident ...

s – found in proteins such as

SNX1 Sorting nexin-1 is a protein that in humans is encoded by the SNX1 gene. The protein encoded by this gene is a sorting nexin. SNX1 is a component of the retromer complex. Function This gene encodes a member of the sorting nexin family. Member ...

, HGS, and EEA1 – bind to PtdIns3''P''. The majority of PtdIns3''P'' appears to be constitutively synthesised by the

class III PI 3-kinase Class III PI 3-kinase is a subgroup of the enzyme family, phosphoinositide 3-kinase that share a common protein domain structure, substrate specificity and method of activation. There is only one known class III PI 3-kinase, Vps34, which is also th ...

PIK3C3 Phosphatidylinositol 3-kinase catalytic subunit type 3 is an enzyme subunit that in humans is encoded by the ''PIK3C3'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of ...

(Vps34), at endocytic membranes.

Class II PI 3-kinases Class II PI 3-kinases are a subgroup of the enzyme family, phosphoinositide 3-kinase that share a common protein domain structure, substrate specificity and method of activation. Class II PI 3-kinases were the most recently identified class of PI 3 ...

also appear to synthesise PtdIns3''P'', their activity however appears to be regulated by a range of stimuli, including growth factors. This suggests that specific pools of PtdIns3''P'' may be synthesised upon cell stimulation.

References

Phospholipids {{Transferase-stub

See also

References