Chapter 23, Problem 7P

Interpretation Introduction

Interpretation:

The consequences of a deficiency in vitamin B₁₂for fatty acid oxidation and metabolic intermediate might accumulate should be explained.

Concept Introduction:

The final product of ß oxidation of fatty acids with odd number of carbon is 3-C propionyl CoA instead of acetyl CoA. Then propionyl CoA is converted into succinyl CoA via several steps.

The carboxylation of a propionyl CoA to produce D-methylmalonyl CoA is the first step. The catalyst for the reaction is a biotin dependent enzyme propionyl CoA carboxylase. In the next step, D-methylmalonyl CoA so formed is isomerized into L-isomer by methylmalonyl CoA epimerase.

This product is then subjected to methylmalonyl CoA mutase reaction which catalyzes the conversion of L-methylmalonyl CoA into succinyl CoA. This enzyme is vitamin B₁₂ dependent.