Why only L amino acids?

[Rafael N Szeinfeld]

	On 6 Jul 1994 6566friedman at vmsa.csd.mu.edu wrote:

> Does anyone have a plausible hypothesis to explain why only L amino 
> acids are used in proteins?  I am teaching an introductory course in 
> biochemistry this summer and this question was raised by a student.  
> Please send your answers to:
> 
> 6566FRIEDMAN at VMS.CSD.MU.EDU
> 
> Alan Friedman
> Dept Biology
> Marquette University
> Milwaukee, WI  
> 
> 
	Hi, 
	May be at the time life began the were an unbalance in the 
concentration of l and d aminoacids, that is [L-aminoacids] > [D-aminoacids]
and so L-aa's were used at that time, thereof L-aa's were selected and so 
they are used up to now.

					Rafael