November 06, 2012

"Homocystine" and "Homocysteine"

"Homocysteine" and "Homocystine"; not just a typing error:

Some of our readers recently commented that our update about Homocystinuria might have contained typing errors. So, before returning to the story of Vitamin B12 and cognition, here is an explanatory note about "Homocysteine" and "Homocystine."


Homocysteine is a four-carbon amino acid with the chemical formula (HS(CH2)2CHNH2COOH):

As we saw in an earlier Blog, Homocysteine comes almost exclusively from dietary Methionine; there are only trace amounts of Homocysteine in foods.  So, what exactly is "Homocystine?"


Put simply, "Homocystine" results when two molecules of Homocysteine combine into a single compound called a dimer.  In the case of Homocystine the dimer consists of two molecules of Homocysteine linked by a disulfide bond, i.e. linked via two sulphur (S) atoms, with loss of two hydrogen (H) atoms.

In our next update, we will look at the early evidence linking Vitamin B12 to memory problems and dementia.

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