After oligosaccharyltransferase transfers Glc3Man9GlcNAc2 to asparagine residues of nascent proteins, the N-glycan is trimmed in the endoplasmic reticulum and then remodelled in the Golgi apparatus. In the ER, glucosidase I (Gcs1) removes the outer glucose and the glucosidase II heterodimer (Gcs2alpha catalytic and Gcs2beta regulatory subunits) removes the two inner glucoses; these steps also control entry into and exit from the calnexin-calreticulin folding cycle. Class I alpha-1,2-mannosidases trim mannoses in the ER and cis-Golgi. In the Golgi, GlcNAc transferase I (Mgat1) adds GlcNAc to the alpha-1,3 arm, which allows alpha-mannosidase II to remove two further mannoses. In insects most N-glycans are then converted to paucimannose glycans by the Golgi beta-N-acetylglucosaminidase Fused lobes (fdl), while a smaller fraction is extended to hybrid and complex glycans by GlcNAc transferase II, core fucosyltransferases, galactosyl-, GalNAc-, glucuronyl- and sialyltransferases.
Boundary. The module starts after transfer of the lipid-linked oligosaccharide to protein (oligosaccharyltransferase is outside the module) and covers ER trimming, Golgi trimming and Golgi diversification, the three FlyBase N-glycan processing groups plus the glucosidase II complex group. Core fucosylation by FutA and Fut6 needs the GlcNAc added by Mgat1 and can occur before or after mannosidase II trimming, so the order within the diversification part is shown only where it is clear. GlcAT-P and GlcAT-S are glucuronyltransferases that act on N-glycans and glycolipids (GlcAT-P is also in the O-GalNAc branch of dmel_protein_o_glycosylation); GalT1 is a beta-1,3-galactosyltransferase. No molecular function is assigned to the regulatory Gcs2beta subunit or to alpha-Man-IIb, whose in vitro activity differs from that of classical mannosidase II. Molecular functions of Gcs1, alpha-Man-Ib and Mgat1 follow orthology; the others are supported by assays of the fly enzymes in GO. FlyBase groups realized by this module: PGERT (FBgg0002122), PGGOT (FBgg0002123), PGGOD (FBgg0002124), GLU2ABII (FBgg0002131). Participants were generated from the FlyBase gene-group membership and mapped to UniProtKB by projects/FLYBASE_GENE_GROUPS/generate_modules.py from module_specs/dmel_n_glycan_processing.yaml. Member genes with a gene review in this repository: alpha-Man-Ia.
All recommended fields populated.
✗ none found
No MODULE:dmel_n_glycan_processing deep-research report alongside the module YAML.
✓ every leaf node grounds to a representative protein.
✓ every declared conforms_to bundle matches its template motif.
✓ every PRECEDES step chains, or its break is acknowledged via chaining_status.
1 gene-function check(s) reflected in core functions · 0 conflict(s) · 11 evidence or coverage gap(s) (12 comparison(s))
Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.
| Annoton | Participant | Function | Assessment |
|---|---|---|---|
| glucosidase_i_gcs1 | Gcs1 UniProtKB:Q9VZ04 Gene |
Glc3Man9GlcNAc2 oligosaccharide glucosidase activity GO:0004573 |
Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. |
| glucosidase_ii_complex/gcs2alpha | Gcs2alpha UniProtKB:A4V4V1 Complex Unit |
Glc2Man9GlcNAc2 oligosaccharide glucosidase activity GO:0106407 |
Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. |
| er_mannosidase_alpha_man_ib | alpha-Man-Ib UniProtKB:Q9VAP8 Gene |
mannosyl-oligosaccharide 1,2-alpha-mannosidase activity GO:0004571 |
Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. |
| golgi_mannosidase_i_alpha_man_ia | alpha-Man-Ia UniProtKB:P53624 Gene |
mannosyl-oligosaccharide 1,2-alpha-mannosidase activity GO:0004571 |
Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass). |
| gnt1_mgat1 | Mgat1 UniProtKB:A1ZBV7 Gene |
alpha-1,3-mannosylglycoprotein 2-beta-N-acetylglucosaminyltransferase activity GO:0003827 |
Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. |
| golgi_mannosidase_ii_alpha_man_iia | alpha-Man-IIa UniProtKB:Q24451 Gene |
mannosyl-oligosaccharide 1,3-1,6-alpha-mannosidase activity GO:0004572 |
Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. |
| paucimannose_formation_fdl | fdl UniProtKB:Q8WSF3 Gene |
beta-N-acetylglucosaminidase activity GO:0016231 |
Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. |
| gnt2_mgat2 | Mgat2 UniProtKB:A0A0B4KHE4 Gene |
alpha-1,6-mannosylglycoprotein 2-beta-N-acetylglucosaminyltransferase activity GO:0008455 |
Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. |
| core_fucosylation_fut6 | Fut6 UniProtKB:Q9VYV5 Gene |
glycoprotein 6-alpha-L-fucosyltransferase activity GO:0008424 |
Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. |
| core_fucosylation_futa | FutA UniProtKB:Q9VUL9 Gene |
glycoprotein 3-alpha-L-fucosyltransferase activity GO:0018392 |
Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. |
| antenna_elongation_beta4galnacta | beta4GalNAcTA UniProtKB:Q7KN92 Gene |
N-acetyl-beta-glucosaminyl-derivative 4-beta-N-acetylgalactosaminyltransferase activity GO:0033842 |
Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. |
| sialylation_siat | Siat UniProtKB:Q9W121 Gene |
beta-galactoside alpha-2,6-sialyltransferase activity GO:0003835 |
Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. |
0 complete review(s) · 1 with deep research · 16 missing review · 0 reviewed but lacking deep research
| Gene | Review | Complete | Deep research |
|---|---|---|---|
| Mgat2 A0A0B4KHE4 | ✗ | — | — |
| GalT1 A1Z8R6 | ✗ | — | — |
| Mgat1 A1ZBV7 | ✗ | — | — |
| Gcs2alpha A4V4V1 | ✗ | — | — |
| alpha-Man-Ia P53624 | ✓ | 14/15 | ✓ |
| alpha-Man-IIa Q24451 | ✗ | — | — |
| beta4GalNAcTA Q7KN92 | ✗ | — | — |
| fdl Q8WSF3 | ✗ | — | — |
| alpha-Man-Ib Q9VAP8 | ✗ | — | — |
| alpha-Man-IIb Q9VF33 | ✗ | — | — |
| Gcs2beta Q9VJD1 | ✗ | — | — |
| GlcAT-S Q9VLA1 | ✗ | — | — |
| GlcAT-P Q9VTG7 | ✗ | — | — |
| FutA Q9VUL9 | ✗ | — | — |
| Fut6 Q9VYV5 | ✗ | — | — |
| Gcs1 Q9VZ04 | ✗ | — | — |
| Siat Q9W121 | ✗ | — | — |
ER and Golgi trimming of protein-linked Glc3Man9GlcNAc2 and its conversion to paucimannose, hybrid and complex N-glycans.