The term chirality refers to the state of one molecule having two steric (3D) configurations, called L (left) and R (right).
Much research is being devoted to find out why the L configuration is the one present in nature, since the solution to this mystery should add to the understanding of biochemistry and of the nuclear forces (in the atomic nuclei).
It was, therefore, surprising to discover that there is one natural D-aminoacid, which is D-serine. It plays a role in the transmition of signals for learning and for memory in the neurons.
It was also discovered that an enzyme is in charge of converting L-serine into the functionally valid D form.
The purpose of the present D-SP mini-essay is raising the following questions:
1.- How can this amazing fact be explained by evolution theory? I have no idea at the present moment; I am asking from readers their collaboration in suggesting a plausible explanation. Because the great mystery is:
How could the physical laws that create what is colloquially called nature, reach by trial and error along thousands of years, the point where D-serine happened to be the right molecule to serve, not just one function, but such a basic one?
2.- In order to make D-serine it was first essential for the enzyme D-serine
racemase to exist. In other words, the essentiality of the unusual D
configuration had to be known beforehand!
I am stopping here. I'll think about a physical explanation, before this essay stokes the fires of creationism: "A supreme intelligence, a master mind, thought about this."
(Just a clue: think of evolution as much complex than you thought until now.)
The aminoacids --the basic components of proteins, which are the fundamentals of life-- are present in nature in the L shape (L-aminoacids), and until now it had been accepted that such is the only one valid for life.
Without D-serine, I would not be writing nor you reading this.