PS, PI, and PG synth and fn Flashcards
What does PS mean
phosphatidylserine
PS accounts for _ of the total PS in mamalina cells
PS accounts for 3-10% of the total PL in
mammalian cells
– PC (60-85%); PE (10-30%)
what are the precursors for PS synth
In mammals, PC & PE are the precursors
for PS synthesis
PS synthesis from PC & PE requires
PS synthesis from PC & PE requires Ca ++
and phosphatidylserine synthase (PSS)
PSS- phosphatidylserine synthases
how many exist in mammals
Two PSS exist in mammals: PSS1 and
PSS2
PSS1 and PSS2 uses
PSS1
uses only PC for PS synthesis, and that
PSS2 uses only PE for PS synthesis
AA sequences bw PSS1 and PSS2
The amino acid sequences between PSS1
and PSS2 are 30% identical, but little is
known about their protein structures and
how they function
where is PSS1 expressed
PSS1 is ubiquitously expressed in vivo
where is PSS2 found
PSS2 is in most PSS1 tissues but highly
expressed in Sertoli cells within testes
PSS1 knockout mice are
PSS1 knockout mice are viable and they
appear phenotypically norma
male PSS2 mice
Male PSS2 knockout mice have smaller
testes and up to half are infertile
However, tissue levels of PC, PS, and PE in the PSS2 knockout tissues
However, tissue levels of PC, PS, and PE
in the PSS2 knockout tissues are normal
The mechanisms that regulate PS synthesis
The mechanisms that regulate PS
synthesis are unknown:
DHA and PS
DHA (22:6n-3) is highly incorporated into PS
within the brain… DHA deficiency reduces
neuronal PS levels
how does PS relate to PSS1 and PSS2 activities
PS appears to directly regulate the enzyme
activities of PSS1 and PSS2:
* high levels of PS reduce the rate of PS synthesis
what does PS activate
PS is required to activate several intracellular molecules
– ie. protein kinase C, sphingomyelinase, and
Na+ /K+ ATPase
where is PS found
PS is typically found intracellularly and on
the inner leaflet of cell membranes
what is the purpose of PS being on theouter cell membrane leaflet
Exposure of PS on the outer cell membrane
leaflet is a marker of cell apoptosis that is
recognized by macrophages (that engulf the
cell)
PI accounts for _ of the total PL in
mammalian cells
up to 10%
how essential is PI
PI is essential for all species
– ie. Deletion of PI synthase in yeast is lethal
What is PI
phosphatidylinositol
where does inositol come from
Inositol comes from either diet or de novo synthesis
– Inositol is synthesized from glucose-6- phosphate
what are the functions of PI
- PI is a precursor to several fast-acting
intracellular signaling molecules,
collectively called phosphatidylinositides - Phosphatidylinositides are derived via the
phosphorylation of the –OH groups on the
inositol head group
PG and its derivatives account for _ of
the total PL in most mammalian cells
<1%
– Exceptions: PG and its derivatives account for
2-18% of total PL in various cell types within the lung – it is a component of lung surfactant
– Cardiolipin is ~15% of PL in cardiomyocytes
