I read in a question I was studying that;
Acetoacetyl-CoA is involved in the b-oxidation of fatty acids

I don't understand where it comes. Could anybody help???

In each round a two carbon fragment is released as acetyl CoA.
In the process of betaoxidation a beta-ketoacyl is formed in each round before the compound is broken into acetyl CoA and an acyl CoA with 2 carbon less than the original.
So, in Beta oxidation of palmityl CoA you have 16 C, after the 1st round you have 14 C and so...
In the last round you have a Beta-ketoacyl of only 4 carbons. This beta-ketoacyl is acetoacetyl CoA, before being broken into two acetyl CoA.

Oh thank you SO MUCH hdu for your clear explanation. So it was in the last portion of oxidation then. I'd better revise it all over again. Thanks again for your input!

try this

http://www.rpi.edu/dept/bcbp/molbioc...1/fatcatab.htm
or
http://www.indstate.edu/thcme/mwking...oxidation.html

Good Luck.

__________________
God Bless You.

H. MD