Breakdown of valine

What are the chemical reactions responsible for the breakdown of valine in the body?


I know oxidative deamination is part of the process but how is valine further broken down from an keto acid to isobutyrate?




From Wikipedia’s article on [propionic acidemia](http://en.wikipedia.org/wiki/Propionic_acidemia):



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> [Enzyme propionyl-CoA carboxylase] is required for the normal breakdown of the essential amino acids valine, isoleucine, threonine, and methionine, as well as certain odd-chained fatty-acids.
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and



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> In healthy individuals, the enzyme propionyl CoA carboxylase converts propionyl CoA to methylmalonyl CoA. This is one step in the process of converting certain amino acids and fats into sugar for energy. Individuals with PA cannot perform this conversion because the enzyme propionyl CoA carboxylase is nonfunctional. The essential amino acids isoleucine, valine, threonine, and methionine and odd-chain fatty acids are simply converted to propionyl CoA, before the process stops, leading to a buildup of propionyl CoA.
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You can find some more or less detailed descriptions of valine’s degradation pathways by Googling:


![enter image description here](https://i.stack.imgur.com/EP1Vh.jpg)


![enter image description here](https://i.stack.imgur.com/Rc28n.png)


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