Flashcards in Lipogenesis Deck (26):
Fatty acid synthesis occurs mainly in the?
Liver and adipose tissue
3 steps of FA synthesis
1)Cytosolic entry of Acetyl CoA (Citrate
2) Malonyl CoA (RLS)
3) FA chain formation
What enzyme converts citrate to oxaloacetate and results in Acetyl CoA in the cytosol?
ATP Citrate Lyase.
Acetyl CoA -> Malonyl CoA
Acetyl CoA carboxylase (RLS) needs Biotin and CO2 requires ATP
hOW IS mALONYL cOa A REGULATOR
It inhibits Carnitine acyltransferase which is the RLS of degradation
Malonyl Coa -> Palmitate
Fatty acid synthase. promoted by Insulin, glucocorticoid hormones, inhited PUFA
Condensation, Reduction, Dehyration, reduction
What are the 2 sources of NADPH
Malic enzyme and PPP
Where are FA elongated passed 16 C long?
Smooth ER, lengthens 2 C at a time using NADPH, use Malonyl CoA,
What carbon donors does SER and Mitchochondria use?
SER: malonyl CoA
mitochondria: acetyl CoA
Humans have 4 desaturases, where are they?
4, 5, 6, 9
Where and how does desaturation occur?
in SER, use NADPH, O2, catalyzed by Acyl CoA Desaturases. Humans cannot synthesize double bond beyond C 9 and 10
Regulation of Desaturases
Induced by Insulin, Suppressed by dietary PUFAs, Dietary cholesterol induces carbon 9 desaturation only
Linoleic acid (18:2 w 6) used to make arachidonic acid
Linolenic acid used to make EPA and DHA
Which FA can diffuse into mitochondria and which need to be actively transported?
Diffuse: SCFA, MCFA
ACTIVE (Carnitine Shuttle): LCFA, VLCFA
What are the enzymes in the Carnitine Shuttle?
1) Fatty acyl CoA Synthetase
2) CPT-1 or Carnitine acyltransferase (RLS) inhibited by Malonyl CoA
3) Carnitine-acylcarnitine translocase- (CACT)
- Antiporter: FA-carnitine in and carnitine out, moves FA-carnitine into intermembrane space
4) CPT-2: Adds CoA, and releases Carnitine
What are the 4 steps of B Oxidation
1) Oxidation: Acyl CoA Dehydrogenase:synth FADH2
3) Oxidation: NADH
4) Thiolysis: Acetyl CoA
MCAD (medium chain Acyl CoA dehydrogenase
most diseases and defects associated with MCAD
4 enzymes in B Oxidation
1) Acyl CoA dehydrogenase
4) acyl tranferase or ketothiolase
What happens with odd number C fatty acids?
1)Becomes Propionyl CoA uses propionyl CoA carboxylase (requires biotin then goes to methylmalonyl CoA
which uses methylmalonyl CoA mutase to go to succinyl CoA which enters TCA cycle
What do you do for B oxidation of unsaturated FA's?
1) Reductases and Isomerases
What about VLCFA'S >20?
Oxidized in the peroxisome. does not produce ATP, produces H2O2
Some key differences in Peroxisomal B-Oxidation and normal
1) 1st step catalyzed by acyl-CoA oxidase
MCAD Deficiency side effects
impairs breakdown of MCFA's, secondary carnitine deficiency, C8 FA builds up in liver, toxic, interferes with urea cycle, Increased urea levels, patient depends on glucose for energy
Where are Ketone bodies synthesized?
Only in the liver.