Other FA oxidation pathways/ketone body metabolism 10/9 (3) Flashcards
where does alpha oxidation occur?
microsomes of brain tissue
why is phytanic acid important?
phytol is found in green veggies, and it has a methyl group on the beta-C so can’t do beta-ox. first, has to do alpha oxidation to remove the methyl on the beta carbon
what is wrong in individuals with Resfum disease?
- their phytanic acid oxidase doesn’t work/is missing
- leads to neurological sympyoms
- caused by genetic defects
- branched methyl groups disrupt myelin structure
omega oxidation
methyl end of the FA is oxidized by 3 enzymes (mixed function oxidase, alcohol dehydrogenase, aldehyde dehydrogenase)
resulting dicarboxylic acid can be beta-oxidized from both ends in mitochondria
differences in beta oxidation in peroxisomes:
- carnitine not involved
- doesn’t make ATP
- very high in liver and kidney
- terminates at C8 CoA (actanoyl CoA) which goes to the mito. for further degradation
- makes H2O2 - gets metabolized by catalase
- acyl CoA oxidase is enzyme used
Zellweger’s syndrome
liver and kidney lack peroxisomes; accumulation of VLCFA in brain tissue
the 3 types of ketone bodies are
- acetoacetate
- beta-hydroxybutyrate
- acetone
rate limiting enzyme in acetoacetate formation
HMG CoA synthetase
mostly made in the liver, making it the most likely place of acetoacetate synthesis
is the reaction from acetoacetate to beta hydroxybutyrate reversible or irreversible?
reversible!
depends on the amount of NADH/NAD
high NADH favors formation of beta hydr.
high NAD favors formation of acetoacetate
how much ATP does acetoacetate generate?
23 net yield ATP
acetoacetate –> AcAcCoA –> 2 acetyl CoA –> 24 ATP - 1 ATP for activation
how much ATP does utilization of one molcule of beta-hydroxybutyrate generate?
26 ATP
23 (from the same pathway as acetoacetate) plus 3 from NADH
during fasting, is KB formation enhanced/decreased?
enhanced! during fasting, increase of fat mobilization/ketogenesis (pyruvate carboxylate is stimulated by Acetyl CoA)
during fasting, oxaloacetate formation is very…
low. this means that acetyl coA doesn’t readily enter the TCA during fasting
in the starvation state, the major energy fuels come from:
ketone bodies
why does jamaican vomiting sickness lead to hypoglycemia?
inhibits FA oxidation which decreases the amount of Acetyl CoA which decreases KB formation–> brain doesnt have sugar!
