Leucine vs. Isoleucine (iso- vs. sec- naming weirdness)

[David513]

Hi all.

I just want to make sure I'm not crazy here...

In orgo, if a side chain had 4 carbons total and one of those carbons was a methyl substituent, we would call it isobutyl if the methyl was on the second carbon and secbutyl if the methyl was on the first.

In biochemistry, all of the sudden we assign isobutyl to be leucine and secbutyl to be isoleucine. Does this not seem confusing and weird to anyone? I assume this is just something I should memorize and stop trying to make sense of, but if anyone has any insight for why this makes sense that would be great.

Cheers!

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[theonlytycrane]

I also thought that this was weird!

I've just been told: "that amino acid is leucine, and the other one is an isomer of leucine = isoleucine."

It still made me question it since the naming seems different than what I learned in organic.

 

[ferrari430man]

I would classify the side chains as isobutyl- and sec-butyl respectively. Idk I could be wrong.

 

[David513]

Ah, you're right! I'll go back and correct my original post to change propyl to butyl.

 

[yeezuswest]

You would think it has to do with the iso/sec- naming from organic chemistry, but it's actually just referring to isoleucine being an isomer of leucine. Source:

https://en.wikipedia.org/wiki/Isoleucine#cite_note-1

 

[shukakuz]

I was literally going to make a post about the weirdness when the suggestion box popped up this post. I was working on my memorization and kept getting messed up with it.