[apo]

> ‘We thought that, in general, all of these amino acids would react similarly because they are structurally similar,’ says Leman. But while almost all the experiments did produce oligomers, the three proteinogenic amino acids reacted more efficiently and produced fewer side products compared with their non-proteinogenic counterparts. ‘That came as a real surprise. We thought “Is this for real?”,’ Leman says.

Looking at the structures, I would not expect similar reactivity:

https://www.pnas.org/content/pnas/116/33/16338/F1.large.jpg?...

They differ in both size and shape. More importantly, they differ in the length of the tether to the positively charged group which could easily play a role in carbonyl activation by this unit, either in the forward direction (peptide formation) or reverse (peptide hydrolysis).

The paper doesn't mention autocatalysis (catalysis of external amino acids or short peptides themselves), but this is also a possibility. There's a large body of synthetic chemistry in which amino acids and short peptides show remarkable catalytic activity.

But the main problem with this study is that peptides are made biologically through catalysis. What we observe in isolated system reactivity has no reason to translate into what's seen in nature because enzymes offer lower-energy transition states.