Folding of D-polypeptide chains into the desired protein conformation is a challenging task, and often requires optimization in a case dependent manner. Protein refolding protocols can be pre-established using the native recombinant Lcounterparts, and they are often sufficient to fold the corresponding D-enantiomer. In the case where disulfide bond formation is involved, oxidants such as cystine or glutathione disulfide can be used. Alternatively, orthogonal protection schemes can be implemented. Most PTM installation can be achieved, particularly the achiral components such as phosphorylation. However, chiral PTMs such as glycosylation largely remains an unresolved synthetic challenge. A plausible solution would be to obtain a mirror-image enzyme (such as endoglycoside hydrolase), capable of assembling the necessary polysaccharide building block from L-sugars, like the enantiomeric polymerase enzymes discussed earlier.