Characterization of a cDNA Encoding a Novel Human Golgi α1,2-Mannosidase (IC) Involved in N-Glycan Biosynthesis
Bibliographic record
Abstract
A human cDNA encoding a 70.9-kDa type II membrane protein with sequence similarity to class I alpha1,2-mannosidases was isolated. The enzymatic properties of the novel alpha1,2-mannosidase IC were studied by expressing its catalytic domain in Pichia pastoris as a secreted glycoprotein. alpha1,2-Mannosidase IC sequentially hydrolyzes the alpha1,2-linked mannose residues of [(3)H]mannose-labeled Man(9)GlcNAc to form [(3)H]Man(6)GlcNAc and a small amount of [(3)H]Man(5)GlcNAc. The enzyme requires calcium for activity and is inhibited by both 1-deoxymannojirimycin and kifunensine. The order of mannose removal was determined by separating oligosaccharide isomers formed from pyridylaminated Man(9)GlcNAc(2) by high performance liquid chromatography. The terminal alpha1,2-linked mannose residue from the middle branch is the last mannose removed by the enzyme. This residue is the mannose cleaved from Man(9)GlcNAc(2) by the endoplasmic reticulum alpha1, 2-mannosidase I to form Man(8)GlcNAc(2) isomer B. The order of mannose hydrolysis from either pyridylaminated Man(9)GlcNAc(2) or Man(8)GlcNAc(2) isomer B differs from that previously reported for mammalian Golgi alpha1,2-mannosidases IA and IB. The full-length alpha1,2-mannosidase IC was localized to the Golgi of MDBK and MDCK cells by indirect immunofluorescence. Northern blot analysis showed tissue-specific expression of a major transcript of 3.8 kilobase pairs. The expression pattern is different from that of human Golgi alpha1,2-mannosidases IA and IB. Therefore, the human genome contains at least three differentially regulated Golgi alpha1, 2-mannosidase genes encoding enzymes with similar, but not identical specificities.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".