October 31, 2012

History of the Discovery of Homocysteine


Homocysteine was discovered in 1932 by Butz and du Vigneaud.  As part of their studies into insulin, they heated an amino acid called "methionine" in sulfuric acid. They discovered that doing so changed methionine into a new amino acid which had similar chemical properties to cysteine. They suggested it should be called homocysteine. Later, du Vigneaud won the 1955 Nobel Prize in Chemistry, partly for his work on this.

Inborn Errors of Homocysteine Metabolism

Over the next few decades a clearer picture began to emerge of how the body breaks down or "metabolises" methionine. Homocysteine was identified as an important intermediate.  The discovery of patients with inherited or "inborn" errors of homocysteine metabolism gave a valuable insight into the roles of enzymes in this process. It was found that many of these enzymes needed B vitamins, including vitamins B12,  B6 and folate, to act as "cofactors" to help them work properly.

Two Cycles, a Pathway and a Branch Point:

This Diagram is an overview of Homocysteine Metabolism. As you can see, Homocysteine sits at a "Branch Point". It lies between a cycle of reactions known as the "Methionine Cycle" and another line of chemical reactions called the "Transsulfuration Pathway."  In short, Homocysteine can either be recycled by the body back to Methionine, or converted into a useful amino acid called Cysteine. 

We will learn more about the roles of Methionine and Cysteine in the body in later Blog Updates. For now, can you spot our deliberate typing errors in the diagram? We have put three in, just to see if you can spot them...and to make you look a little closer at the Biochemistry of Homocysteine!

Well, that is more than enough Biochemistry to take in for now! In our next Blog updates we will turn to look at dementia, including the history of Alzheimer's Disease and its socioeconomic burden.

Check back soon for further updates.

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