Chemoenzymatic Synthesis of Glycopeptides Bearing Galactose–Xylose Disaccharide from the Proteoglycan Linkage Region

Abstract

Proteoglycans have important biological activities. To improve the overall synthetic efficiency, a new chemoenzymatic route has been established for the proteoglycan linkage region bearing a galactose-xylose disaccharide. The xylosylated glycopeptides were synthesized via solid phase synthesis, which was followed by the addition of the galactose unit by the galactosyl transferase β4GalT7. This work leads to a better understanding of the acceptor preference of β4GalT7 and opens the door for expeditious synthesis of the proteoglycan linkage region.

Exploration of human xylosyltransferase for chemoenzymatic synthesis of proteoglycan linkage region

“…19 To test whether the enzymatically prepared xylosyl peptide is a viable substrate for β4GalT7, xylosylated peptide 8 was treated with β4GalT7 and UDP-Gal (Scheme 2a). The glycopeptide 14 19 with two Gal-Xyl disaccharides was successfully produced in 77% yield. Thus, the overall yield for the stepwise conversion of 4 to 14 with XT-I glycosylation followed by β4GalT7 reaction was 53%.…”

“…Encouragingly, a full conversion of acceptor peptide 4 was observed with an isolated yield of 68% for glycopeptide 14. Besides peptide 4, this one-pot two-enzyme (OP2E) protocol smoothly converted peptides 3, 5, and 6 to the corresponding glycopeptides 15-17 19 (Figure 2) with higher yields compared to the stepwise synthesis (Table 4). The polyhistagged hCD4420-178 protein was also glycosylated by the OP2E method to yield the Gal-Xyl modified CD44 (Figure S15).…”

“…HRMS and nuclear magnetic resonance (NMR) analyses confirmed the structure of the β-glycosylated product ( 1 JC1, H1 =159.5 Hz), 18 which was identical to the chemically synthesized glycopeptide 2. 19 Scheme 1. XT-I-catalyzed xylosylation of bikunin peptide 1.…”

Expeditious Synthesis of a Glycopeptide Library

“…GP synthesis can be combined with chemoenzymatic approaches, but such processes are very sensitive to reaction conditions and have several limitations. [22,23] Other solid-phase methods reported recently also require a large excess of GAAs and are very timeconsuming. [24,25] Using pre-synthesized GAAs has several setbacks (Figure 1A).…”

“…Using GAAs for GP synthesis is the most popular strategy, as it allows the installation of the glycan moiety in a precise location on the peptide by iterative SPPS steps. GP synthesis can be combined with chemoenzymatic approaches, but such processes are very sensitive to reaction conditions and have several limitations [22,23] . Other solid‐phase methods reported recently also require a large excess of GAAs and are very time‐consuming [24,25] …”