The carbonyl carbon is subsequently attacked by the electronegative oxygen.

Cys-25 then performs a nucleophilic attack on the carbonyl carbon of a peptide backbone.

Lacking this stabilization, the carbonyl carbon of p-hydroxy compounds is less electrophilic.

A sulfur from a cysteine in the active site makes a nucleophilic attack on the carbonyl carbon of the aldehyde.

It is the backbone carbon before the carbonyl carbon.

Therefore, the carbonyl carbon becomes electrophilic, and thus more reactive with nucleophiles.

The sp-hybridized isocyanide carbon becomes the carbonyl carbon of the product.

The original carbonyl carbon is acidified by its proximity to the phosphonate group.

Water replaces the N-terminus of the cleaved peptide, and attacks the carbonyl carbon.

The now electron-deficient carbonyl carbon re-forms the double bond with the oxygen.