[verheesen]

Can anyone help me out. I'm a doctor and besides the fact I don't understand we work far more together with chemists to unraffle physology I got a question concerning stereochemistry.
It is known that amino acids have enantiomers and they exist in nature and within the human body. Only in bacteria some D-amino acids are found in cell walls. So it looks like they don't have a function but that's hard to believe. Probably we don't recognize their functions yet.

Can anybody tell me how chemists think about this phenomena and especially what they think their function is. And can that function be translated to the human body and they chemical processes within?

Secondly it is known that this isomerization takes place in humans. The why question I already asked but I would like to know how it takes place. What factors are triggering this isomerization? Is it regulated by enzymes, do micronutrients play a role? Can concentration differences induce this process?
Thanks for any answers

Richard Verheesen

[sjb]

Can anyone help me out. I'm a doctor and besides the fact I don't understand we work far more together with chemists to unraffle physology I got a question concerning stereochemistry.
It is known that amino acids have enantiomers and they exist in nature and within the human body. Only in bacteria some D-amino acids are found in cell walls. So it looks like they don't have a function but that's hard to believe. Probably we don't recognize their functions yet.

Well, a bacterium's job is to survive, basically, and anything that helps that helps the population as a whole. As you point out, most of the amino acids in nature are L, so that means enzymes have developed to selectively cleave the peptide bonds in these proteins. The same enzymes will have a limited effect on D-amino acid chains.

Can anybody tell me how chemists think about this phenomena and especially what they think their function is. And can that function be translated to the human body and they chemical processes within?

Secondly it is known that this isomerization takes place in humans. The why question I already asked but I would like to know how it takes place. What factors are triggering this isomerization? Is it regulated by enzymes, do micronutrients play a role? Can concentration differences induce this process?

I'm not really sure about concentration differences, but isomerisation typically goes through planar intermediates, such as the ene-diol in the glucose  fructose step in the glycolysis pathway. So in that regard, micronutrients may play a part, as part of these enzymes...