I want to know why the organisms used L form amino acids instead of D form amino acids and why they cannot use L form sugars..
The homochirality in biology is the subject of much debate. See: Meierhenrich (2008). Amino acids and the asymmetry of life. Springer, Heidelberg, Berlin, New York. ISBN 3-540-76885-8.
Most scientists believe that Earth life's "choice" of chirality was purely random, and that if carbon-based life forms exist elsewhere in the universe, their chemistry could theoretically have opposite chirality.
Some suggest that early amino acids could have formed in comet dust. In this case, circularly polarised radiation (which makes up 17% of stellar radiation) could have caused the selective destruction of one chirality of amino acids, leading to a selection bias which ultimately resulted in all life on Earth being homochiral.
Enzymes, which are chiral, often distinguish between the two enantiomers of a chiral substrate. Imagine an enzyme as having a glove-like cavity that binds a substrate. If this glove is right-handed, then one enantiomer will fit inside and be bound, whereas the other enantiomer will have a poor fit and is unlikely to bind.
A conundrum for anyone studying the prebiotic world is why D-sugars are the natural isomers, whereas natural amino acids have the L-configuration.
This paper suggests how carbohydrates could have formed in prebiotic conditions by producing (D)-erythrose and (D)-threose sugars with (L)-amino acid catalysts. Evolution should have selected the most efficient processes by then.
http://pubs.rsc.org/en/content/articlepdf/2012/ob/c1ob06798b
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