text: Modification after heptapeptide backbone formation
  Once the heptapeptide backbone has been formed, the linear enzyme-bound intermediate is cyclized. Gene disruption studies indicate cytochrome P450 oxygenases as the enzymes that performs the coupling reactions. The X-domain in the final NRPS module is required to recruit the oxygenase enzymes. OxyB forms the first ring by coupling residues 4 and 6, and OxyE then couples residues 1 and 3. OxyA couples residues 2 and 4, followed by the formation of a C-C bond between residues 5 and 7 by OxyC.  The regioselectivity and atropisomer selectivity of these probable one-electron coupling reactions has been suggested to be due to the folding and orientation requirements of the partially crossed-linked substrates in the enzyme active site.  The coupling reactions are shown below.
  Specific glycosylation has been shown to occur after the formation of the heptpeptide aglycone. Three separate glycosyl transferases are required for the glycosylation of the teicoplanin aglycone.  Tei10* catalyses the addition of GlcNAc to residue 4, followed by deacetylation by Tei2*. The acyl chain (produced by the action of Tei30* and Tei13*) is then added by Tei11*. Tei1 then adds a second GlcNAc to the β-hydroxyl group of residue 6, followed by mannosylation of residue 7 catalysed by Tei3*.