# Are imine or amine bonds similar to ethereal bonds, from the perspective of an enzyme?

I'm interested in enzymes that can cleave (hydrolyse or however) an ethereal bond ($\ce{C-O-C}$). Enzymes can evolve to act on chemicals/bonds that are similar to what they previously acted on, so enzymes with similar functions are also interesting.

I've been told by a couple of chemists that carbon-nitrogen-carbon bonds are similar to ethereal, so I was wondering if, and in what way that is true. Are the bonds in an imine group ($\ce{C-N=C}$) or a amine group ($\ce{C-NH-C}$), more similar to those in an ethereal group compared to a $\ce{C-C}$ pair, for example?

I guess from the perspective of an enzyme, if you were approaching the imine from the direction of the lone pair, that would feel pretty similar to an oxygen maybe?

• See, some enzymes are awfully picky about their substrates, some are less so. – Ivan Neretin Sep 2 '16 at 13:53
• I was asking about two different nitrogen groups, but I wasn't sure of the names. I think the question now says what I meant – JCThomas Sep 2 '16 at 14:33
• @IvanNeretin Yeah, I guess my question was how unpicky would an enzyme need to be to act on both, or switch substrate. I've noticed different isochorismatases that act on a nitrogen or oxygen, but they don't have much sequence similarity so that might not mean anything. – JCThomas Sep 2 '16 at 15:02

However, note that the carbons next to ether and amine bonds have four atoms attached to them (two hydrogens and another carbon each), while the imine has only one hydrogen. The $\ce{C=N}$ bond is planar, meaning that the configuration of the neighbouring atoms is also relatively fixed. Thus, the imine may have a pretty different shape — and may not fit into the enzyme’s active pocket. This might actually also mean that the imine cannot accept the hydrogen bond offered by the enzyme because it cannot orient itself favourably.
All these heteroatom bonds are clearly different from $\ce{C-C}$ bonds due to the bonds’ inherent polarity (electronegativity of $\ce{O}$ and $\ce{N}$).