Free Online lectures on Biochemistry for Medical and Allied Health Sciences students by Biochemistry Club
- or even chain fatty acids 4-C fatty acid remains at the end in beta-oxidation which is then cleaved to form 2 Acetyl CoAs.
- But in less than 1% of odd chain fatty acids (17-19 C), at the end they end up with 5-C Acyl CoA.
- One Acetyl CoA is removed and remaining ends up in 3-C, acyl CoA called Propionyl CoA.
- Propionyl CoA can also be formed by oxidative degeneration of amino acids valine and isoleucine.
- Methionine & threonine can also form propionyl CoA.
Steps of Oxidation of Odd chain fatty acids
- 3-C Propionyl CoA is converted into 4-C Methylmalonyl CoA by the addition of CO2 with the help of enzyme Propionyl CoA Carboxylase.
- In this reaction one ATP is used and Biotin acts as a coenzyme.
- 4-C Methylmalonyl Co A is converted into 4-C Succinyl CoA with the help of enzyme Methylmalonyl CoA Mutase.
- In this reaction Vitamin B12acts as a coenzyme.
- Succinyl CoA can enter the Krebs cycle.
- In even chain fatty acids none of the carbons end up in Glucose.
- But in odd chain fatty acids oxidation the last 3 carbons can be used to make Glucose as the form Succinyl CoA which enters the Krebs Cycle.
Pathology associated – Vitamin B12 Deficiency
- Defect in the last step causes accumulation of Methylmalonic acid in blood.
- This is known as Methylmalonic acidemia.
- It then starts appearing in urine – Methylmalonic aciduria.
- There are 4 reasons of the defect in the last step.
FOR COMPLETE LECTURE PLEASE VISIT THE COURSE PAGE IN BIOCHEMISTRY II SECTION. CLICK THE CURRICULUM TAB TO VIEW FULL LIST IN METABOLISM OF LIPIDS.