https://phys.org/news/2019-02-physical-effect-year.html

 

I used to work in the industrial enzyme business. Enzymes are just like other proteins except that they're catalytic for specific chemical reactions.

Virtually all the proteins and enzymes mankind has ever dealt with are made up of L amino acids, and glycine which is non-chiral. There are no R (or more properly "D" for dextro) amino acids in nature.

As a market development guy charged with planning our enzyme R&D, the "what if" of putting D amino acids into enzyme sequences always intrigued me. What new enzyme properties might be possible? Could you improve stability or specificity? These things have large commercial value, so I suspect someone will answer these questions. Perhaps it's been done by now.

 

Here's a nice short review of chirality and the more recent R & S system.

https://www.masterorganicchemistry.com/2017/05/24/d-and-l-sugars/

In the R & S system, most L-amino acids are S, except cysteine because the atomic number of sulfur over-rides the carbons/oxygens as one counts clockwise or counterclockwise at the chiral center.

As that link points out, Emil Fischer arbitrarily assigned D & L and happened to guess right. The major problem with the D & L system is relating non-sugar structures back to glyceraldehyde. For example, different synthetic routes can result in different assignments. One of my treasures is a picture of Emil Fischer that is autographed by his daughter when she visited our department many years before I got there.. I rescued it from what was about to be trash while a student.