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38 Cards in this Set

  • Front
  • Back
FA storage
de novo synthesis in liver from glucose
FA degradation (TG's)
3FA's and one glycerol,

FA's go to liver ATP/NADH gluconeogenesis

to muscle spares glucose for glucose dependent tissues
Describe degradation TG to FA in adipose and transport to appropriate tissues
glucagon/epi activates HSL (hormone sensitive lipase, it's P'd)

TG-->3FA and glycerol(liver)

FA goes out of adipocyte to blood and is bound to albumin

goes to target tissue dissociates and binds to FABP
What tissue can FA not go to?
FA transport into mitochondria once it hits target tissues
has to be activated by tagging an acetyl on it, and has to be transported via citrate (except SCFA and MCFA)
where do SCFA and MCFA's get activated?
in the mitochondrial matrix
what activates FA's?
Fatty acyl-CoA synthetase, uses two high E bonds, driven by pyrophosphatase,

families of synthetases are based on chain length
Where does activation of LCFA and VLCFA's occur?
mitochondrial intermembrane space (cytosol?)
describe biochemically, the transport of activated FA into mito
FA-SCOA --> FA-Carnitine

via CAT I
what is CAT I inhibited by?

lots of malonyl-CoA means synthesis is happening in the cytosol, so dont want to transport newly made FA into mito for degradation
rate limiting and regulated
rare: CAT I II and translocase

decreased syn (in premies)
defective membrane transporter in muscle heart kidneys

treatment: aviodance of fasting, low LCFA intake, supplement with MCTG and carnitine
Beta oxidation of palmitic acid
palmitic acid(16:0) + 7 FAD + 7 NAD --> 8 acetyl coa + 7 FADH2 + 7 NADH
beta oxidation of stearic acid
stearic(18:0) --> get 8 fadh2 8 nadh 9 acetylCoA
steps of beta-oxidation
FAD-deH (trans dbl bond between alpha and beta)

enoyl CoA Hydratase ( add water, get OH on beta C)

beta-hydroxyacyl CoA DeH-NAD
(double bond carboxy on beta C)

Beta-ketoacyl CoA thiolase ( cleave at beta C, add CoASH)
which beta oxidation enzyme is chain-length specific

which transport enzyme is chain length specific
acyl CoA DeH-FAD

fatty-acyl CoA synthetase (makes FA-SCoA)
for LCFA beta-oxidation what enzymes are in a membrane bound complex?`
enoyl CoA hydratase
beta-hydroxyacyl CoA DeH-NAD
Beta-ketoacyl CoA thiolase

(the last 3)
what regulates beta oxidation (3)
substrate concentration

malonyl Coa(inhibits CAT I)

AcetylCoA/ free CoA ratio (thiolase uses free CoA in the last step, so decreased free CoA means decreased beta ox)
what does a high I/G ration do for FA synthesis? for beta-oxidation?
high I/G increases synthesis and decreases oxidation
key regulated enzyme(s) of FA synthesis? or oxidation?
synthesis: acetyl CoA carboxylase (makes malonyl coA, uses biotin PG)

oxidation: CAT I
how many ATP per C do you get for beta oxidation of FA? how many from glucose?
8atp/C for FA

6 atp/C for glucose
Beta oxidation of odd-numbered FA's
problem - 3C product eventually, left with propionyl CoA

add a C: CO2 ATP / Proprionyl CoA carboxylase biotin

change from D to L: methylmalonyl CoA racemase

change L-methylmalonyl CoA to succinyl CoA: methylmalonyl mutase Coenz B12
what is the only glucogenic precursor from FA's?
proprionate getting changed to succinyl CoA for the TCA cycle
Beta-oxidation of unsaturated FA's

dbl bond at odd C
problem: enoyl hydratase can't work on a cis kinked double bond

cleave normally till hit double bond

use enoyl isomerase to transform cis dbl bond at 3 to trans dbl bond at 2
beta ox of unsaturated

dbl bond at even C
beta oxidize till hit dbl bond at C4, and start initial deH of cycle 5 by making dbl bond (trans) at alpha-beta C

use nadph and dienoyl CoA reductase to make trans dbl bond at beta-c3

shift trans dbl bond at 3 to C2 using enoyl isomerase

this can then be used by enoyl CoA hydratase to finish cycle
what is required for VLCFA oxidation?
peroxisome - specific fatty acyl CoA synthetase

ABC transporter (into perox)

oxidase (direct reduction of O2)
draw out VLCFA degradation
VLCFA --> FA-SCoa (synthetase)

FA-SCoa --> enoyl-SCoa (FAD-oxidase)

Enoyl CoA -->BOH CoA(hydratase)

BOH --> beta Keto (DeH/get NADH)

Thiolase --> acetylCoA and eventually break down to MCFA

MCFA is transported out to mito via peroxisomal CAT (uses carnitine, generates CoA)
Peroxisomal alpha oxidation of FA
occurs at alpha b/c beta has a branch on it
shortens by 1C (CO2)

phytanic acid (20C) to pristanic acid (19)which can do beta oxidation
how else can you ox branched FA?
minor pathway
oxidation of methyl terminus (omega -ox)
Synthesis of ketone bodies
FA-> B-oxidation-> acetyl CoA

2AcetylCoA (2c) --> acetoacyl Coa(4c) + CoA

acetoacyl Coa --> HMG coa (6c)+ CoA (HMG synthase)

HMG Coa --> acetoacetate + acetyl CoA (HMG lyase)

acetoacetate + NADH <-> BOH butyrate(BOH DeH)

acetone can be produced but its a dead end
how many CoA's do you get? from KB synthesis

what do you use
2 CoA

3 acetyl CoA's (regenerate 1)
1 NADH (interconversion from acetoacetate to BOH)
Regulation of KB synthesis
CoA supports B-oxidation
NADH from B-oxidation pushes acetoacetate to BOH
Utilization of KB (not by liver!)

BOH -> acetoacetate+NADH (BOH deH)

acetoacetate + Succinyl CoA --> acetoacyl CoA + Succinate (transferase)

acetoacyl Coa + Coa <-> 2 Acetyl Coa (thiolase)
what is resting [KB]?

diabetic ketoacidosis[KB]?
3-5 mM

up to 20 mM
defect in ABC transporter for prox

can't get VLCFA's into perox

accumulate (esp in brain)

childhood form: develops normally till school age, then dementia, adrenal insufficiency
Zellweger cerebrohepatorenal syndrome
VLCFA and phytanic acid accumulation
low survival
PEX Receptor found on the surface of peroxisomes recog's SKL on proteins
Refsum disease
phytanic acid storage disease (alpha-ox)

defic in alpha-hydroxylase

restrict dietary phytanic acid
medium chain acyl-CoA DeH

most common defect in B-oxidation

usually less than 2, can die

under 12C oxidation is greatly reduced,
Hypoketosis and hypoglycemia (more glucose use cause no KB, and little gluconeogenesis b/c ATP and NADH to drive gluconeo come from beta-ox

diagnosis: peal of carbons at c8

treatment: avoid fasting, carnitine supplementation, newborn screening