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I want to design an alien species whose physiology is capable of metabolizing substances regardless of whether their chemical chirality is levorotatory or dextrorotatory. Is this scientifically possible, and if so, what would be required?

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    $\begingroup$ Do you want their metabolism to break down both kinds of molecules (that would be relatively easy), or do you want them to incorporate both kinds into their bodies without change (that should be harder)? $\endgroup$ – Alexander Jul 12 '17 at 0:16
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    $\begingroup$ Possible, or expected to happen? For example, you would need an additional genes to be able to burn L-Glucose. And additional set to create it. This is hug cost, evolutionary, and also it would be surprising to happen. And it does not provide a plant with any benefit, one kind of glucose can do the job. $\endgroup$ – Mołot Jul 12 '17 at 0:27
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    $\begingroup$ Which molecules? Some are already present both ways! en.wikipedia.org/wiki/Carvone $\endgroup$ – JDługosz Jul 12 '17 at 1:31
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    $\begingroup$ @MarqFJA87 - so, suppose your species utilize L-molecules directly. Then they can develop enzymes that break down D-molecules and use them as fuel. $\endgroup$ – Alexander Jul 12 '17 at 2:43
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    $\begingroup$ Some life forms already incorporate D-amino acids along with the normal L-ones (ask your nearest friendly E.coli about this), so limited heterochirality is already a part of Earth biology, and can have evolutionary value (the classic D-Ala-D-Ala linkage of peptidoglycan is an example of this -- if it were an L-amino-acid linkage, then the bacteria's wall would just get eaten up by whatever proteases were roaming around) $\endgroup$ – Shalvenay Jul 12 '17 at 3:24
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Its not going to be a problem. Humans and animals already have some ability to digest D-isomers of amino acids (though results significantly vary from one amino acid to another). In a world where D-isomeres are widely available, it's logical to assume that animals would have the necessary enzymes to process not some, but all D-isomers.

This is all assuming that the species of this world, like here on Earth, would have a strong preference for one type of enantiomers. So, some species would like D-isomers, some L-isomers, and they can be a viable food source for each other.

Study abstract 1

Study abstract 2

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