FA synthesis Flashcards
what are the two preparatory steps of FA synthesis
formation of malonyl CoA
binding of acetyl CoA and MalonylCoA to FAS1
what enzyme makes malonyl CoA
acetyl CoA carboxylase
what requires two forms of chemical energy
Biosynthesis of FA
how is citrate moved to the cytoplasm to make acetyl CoA
citrate transporter
how do we get from citrate to acetyl coa
citrate lyase transfers acetyl group to CoA
where is NADPH sources from for reduction reactions
PPP and malic enzyme
what does the second preparatory step lead to the release of
CoA
what do acetyl coa and malonyl coa connect to FAS via
thioester linkage
what adds acetyl CoA group onto SH group of ACP
MAT
where does MAT move acetyl coa to
SH group of ACP
what happens after acetyl coa is moved to ACP
it is transfered to SH group of KS
what happens after acetyl coa is moved to KS
MAT moves malonyl cao to SH of ACP
what is the last step in preparation for step 1 for FA synthesis
MAT moves malonyl cao to SH of ACP
what does ACP contain
4’-phosphopantetheine
what is 4’-phosphopentathiene
prosthetic group on ACP AND CoA that serves as a flexible arm, tethers FA chain to surface of FAS and carries reaction intermediates from one active site to the next
moving malonyl groups to SH group name
esterification
what form of acyl group is on KS
activated acyl group
what happens in the first condensation step of FA synthesis
activated acyl group and 2C from malonyl CoA undergo condensation to form a acetoacetyl ACP
CO2 leaves and the acyl chain is extended by 2 carbons
what is formed in the second step of FA synthesis- reduction
B keto product is reduced to an alcohol
what is the B keto product
acetoacetyl ACP
what catalyzes the reduction recation of FA synthesis
B ketoacyl-ACP reductase/ KR
what is required for the reduction step of FA synthesis
B ketoacyl-ACP reductase/ KR and NADPH as electron donor
what specifically happens to the carbons in the reduction step
reduction of carbonyl group at C3 to from D- B- hydroxybutyryl-ACP
what is the third step in FA synthesis
dehydration
what enzyme catalyzes the third step in FA synthesis
B-hydroxyacyl-ACP dehydratase/ DH
what is formed by step 3 and how
trans-delta2-butenoyl-ACP by removing H20 elements from C2 and C3 of b-hydroxybutyryl-ACP
4th step of FA synthesis
reduction
what enzyme cataylyzes the 4th step
enoyl-ACP reductase/ ER
what does enoyl-ACP reductase/ ER do
catalyzes reduction of DB of trans delta2-butenoyl-ACP to form butyryl ACP
how do we set up for the next pass of FA synthesis
transfer of butyryl group from ACP to KS
recharging ACP with new malonyl COa
where is C16 derived from
methyl carbon atom of the acetyl Coa used to initially prime the system
where is C15 derived from
carboxyl carbon atom of the acetyl Coa used to initially prime the system
what is 16:0 called
palmitate
how many cycles of FA (4 steps) does palmitate go throu
7
what releases palmitate
hydrolysis of thioester linkage by thioesterase/ TE
what does TE do
hydrolizes the thioester linkage
what regulates FA synthesis
ACC phosphorylation
level of gene expression by AAC and FAS
inhibition of FA synthesis and oxidation occuring together by malonyl CoA
how does malonyl coa inhibit futiile cycle
inhibits FA import into mitochondria to ultimately shut down B oxidation
what does ACC cause
polymerization into long inactive fillaments
what is the rate limiting step of FA synthesis
ACC phosphorylation
what is the precursor of long chain saturated FA
palmitate
FA elongatino systems lengthen…
palmitate
where does the lengthening of palmitate occur
in the smooth ER and mitochondria
what is the most common product of lengthening of palmitate occur
stearate 18:0
what enzyme is required for the desaturation fo FA
fatty acyl CoA desaturase
what does fatty acyl CoA desaturase do
catalyzes oxidative reaction indoducing double bond
what does desaturation of FA require
NADPH, cyt b5, and cyt b5 reductase
what accepts electrons in the desaturation of FA
O2 accepts 2 electrons from saturated FA and 2 electrons from cyt b5
what desaturases do humans have
4,5,6,9 but not beyond 9
what can desaturate positions beyond C9
plants
what are the essential FA
linoleate and a linolenate
what is linoleate
18:2 w-6
where are linoleate double bonds
9 and 12
a linolenate
18:3 w3
where are a linolenate duoble bonds
9,12,15
what do PUFAs do
help control membrane fluidity
where are cholesterols acrbon atoms provided by
acetate
what is essential intermediate for the pathway of cholesterol synthesis
isoprene units
what are the stages in cholestrol synthesis
condensation
mevalonate to activated isoprene units
polymerization of 6 isoprene units to form 30 carobn linear squalene
cyclization of squalene to from 4 rings of steroid nucleus
what are two descriptive words for FA synthesis
endergonic and reductive
what is ACP recharged with after one round of FA synthesis
malonyl CoA
what is formed from the reduction step
D-B hydroxybutyryl- ACP
what does DH stands for
D-B hydroxyacyl ACP dehydratase
what is formed by the dehydratino step
trans delta2 butenoyl ACP
how many cycles of FA synthesis did palmitate go through
7
what activates and inactivates ACC
citrate activates it
epinephrine phosphorylation and inactivation
glucagon phosphorylation and inactivation
high [AMP] phoshorylation and inactivation
palmitoyl CoA inactivates it
what occurs in smooth ER and mitochondria
FA elongation systems
where do FA elongation systems happen
in mitochondria and smooth ER
what enzyme is used for FA desaturation
fatty acyl coa desaturase
what does FA coa desaturase require
NADPH, cytb5, cytb5 reductase
role of PUFAs
control membrane fluidity
