Writing: Input Wanted Alien chiral chemistry

AI Thread Summary
The discussion centers on the concept of chirality in biology, particularly how terrestrial organisms utilize specific enantiomers while the 'Other Hand' enantiomers remain largely bio-unavailable or toxic. It posits that alien biology, shaped by different evolutionary paths, could potentially utilize these 'Other Hand' enantiomers differently. The conversation explores whether terrestrial fungi and bacteria can use these non-standard enantiomers without degradation, noting that while our biological systems favor one chirality due to energetic preferences, some bacteria are known to incorporate wrong-handed amino acids into specialized structures like antibiotics and cell wall components. The existence of enzymes, such as racemases, that can handle these non-standard amino acids suggests that some bacteria can directly utilize them rather than merely breaking them down. This raises questions about the metabolic pathways and ecological roles of these non-standard amino acids in microbial life.
Nik_2213
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A lot of terrestrial biology has specific chirality, the 'Other Hand' being bio-unavailable or toxic...
As 'our' set is product of aeons of happenstance and evolution, alien biology probably differs.
( I'm thinking genuinely alien 'alien' rather than eg 'seeding' or panspermia...)
Can terrestrial fungi / bacteria use 'Other Hand' enantiomers as-is, without degrading to simpler ?
 
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I don't see why not. I have read that our chirality is very slightly favored energetically. I've never been sure to believe it or not.
 
Hornbein said:
I don't see why not. I have read that our chirality is very slightly favored energetically. I've never been sure to believe it or not.
"Why" might be "because they don´t produce much of them".
But even if living enzymes did not produce or use wrong handed amino acids, some of them are formed by purely abiological racemization reactions from left handed enantiomers. If nobody at all ate or used them, they would build up.
In fact, several bacteria do use nonstandard, including wrong handed amino acids. They put them in specialized places like antibiotic oligopeptides and cell wall glycopeptides. Nonstandard amino acids including wronghanded ones are refractory in that standard enzymes designed for standard amino acids often fail at them. But some bacteria do have enzymes specialized for nonstandard amino acids... including wrong handed amino acids. One group of enzymes specialized for wrong-handed amino acids is "racemases".
When bacteria meet supplies of wrong handed amino acids, do they just break them down, or use directly for their specialized products (antibiotics, cell wall glycopeptides)?
 

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