22.6 The Elongation and Unsaturation of Fatty Acids Are Accomplished by Accessory Enzyme Systems

Membrane-bound Enzymes (Complex):

 
 

NADH-cytochrome reductase,

cytochrome b5,

desaturase

 
 

*This oxidase complex catalyses formation of oleoyl coA from stearoyl coA (see p.634 Fig 22.32)

 
 

Eucosanoid hormones:

 
 

• Prostaglandins,
  
• prostacyclins,
  
• thromboxanes,
  
• and leukotrienes
  

   
   

  They are synthesized from Arachidonate
  

   
   

  Eucosanoids are local hormones that stimulate inflammation, regulate blood flow to particular organs, control ion transport across membranes, modulate synaptic transmission, and induce sleep.
  

   
   

  Aspirin block active site of prostaglandin synthase.
  

22.5 Acetyl CoA Carboxylase Plays a Key Role in Controlling Fatty Acid Metabolism

Acetyl CoA Hormone Regulation

Glucagon, epinephrine, and insulin

Insulin stimulates fatty acid synth by activating carboxylase, whereas glucagon and epinephrine have the reverse effect

//Active carboxylase - Dephosphorylated

AMPK phosphorylates it. AMPK is activated by AMP and inhibited by ATP. Carboxylase inactivated when E charge is low

22.4 Fatty Acids are Synthesized and Degraded by Different Pathways

Fatty Acid Synthesis Consists of a Series of Condensation, Reduction, Dehydration, and Reduction Reactions

D rather than L isomer is formed in fatty acid synthesis.

NADPH is consumed in biosynthetic reactions, while NADH is generated in energy-yielding reactions

Thioesterase hydrolyses C16-acyl ACP to yield palmitate and ACP

Elongation by fatty acid synthase complex stops on the formation of palmitate (c16)

Several Sources Supply NADPH for Fatty Acid synthesis

Draw reaction mechanisms for Figure 22.27 p.639 (Reaction equations help)

Understand Pathway Integration for Fatty Acid Synth

Read chapter on Pentose Phosphate Pathway