Cholesterol Synthesis

Cross references:  Cholesterol     Coenzyme A    

"Ontogeny recapitulates phylogeny" is a catchy phrase coined by Ernst Haeckel, a 19th century German biologist and philosopher to mean that the development of an organism (ontogeny) expresses all the intermediate forms of its ancestors throughout evolution (phylogeny).

Ontogeny Recapitulates Phylogeny   

Recapitulation theory - Wikipedia   
    My comment
Professional biologists feel compelled to prove their intellectual purity by denying that "ontogeny recapitulates phylogeny".  Since I'm not a professional biologist, I'm not under any similar restraint.  As a working hypothesis, I will assume that the biosynthesis of cholesterol  parallels, and helps us understand, the evolution of cholesterol. 

I've used the 
I was only partially successful.  Even when a precursor is relatively simple, the enzyme(s) which facilitate its reactions might be quite complex.  In retrospect, I realize that I shouldn't have been surprised.  Life on this planet began approximately 4 billion years ago, but we know almost nothing about the first 3.5 billion years.  I now understand that much of the complexity that we see today developed during that first 3.5 billion years.   

Cholesterol Synthesis   
     "Hydroxymethylglutaryl-coenzyme A (HMG-CoA) is the precursor for cholesterol synthesis.

HMG-CoA is formed by condensation of acetyl-CoA and acetoacetyl-CoA, catalyzed by HMG-CoA Synthase."

    My comment
So it seems that acetyl-CoA and acetoacetyl-CoA  are the two initial building blocks leading to Testosterone  .  However, it turns out that coenzyme A is almost as complex as cholesterol.  So we haven't made much progress in our search for the simple precursors of testosterone.    

Coenzyme A - Wikipedia   
Coenzyme A (CoA, CoASH, or HSCoA) is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle. All genomes sequenced to date encode enzymes that use coenzyme A as a substrate, and around 4% of cellular enzymes use it (or a thioester, such as acetyl-CoA) as a substrate. "  

Coenzym A.svg