Molecular and Biochemical Analysis of Two β-Galactosidases from<i>Bifidobacterium infantis</i>HL96
Bibliographic record
Abstract
Two genes encoding beta-galactosidase isoenzymes, beta-galI and beta-galIII, from Bifidobacterium infantis HL96 were revealed on 3.6- and 2.4-kb DNA fragments, respectively, by nucleotide sequence analysis of the two fragments. beta-galI (3,069 bp) encodes a 1,022-amino-acid (aa) polypeptide with a predicted molecular mass of 113 kDa. A putative ribosome binding site and a promoter sequence were recognized at the 5' flanking region of beta-galI. Further upstream a partial sequence of an open reading frame revealed a putative lactose permease gene transcribing divergently from beta-galI. The beta-galIII gene (2,076 bp) encodes a 691-aa polypeptide with a calculated molecular mass of 76 kDa. A rho-independent transcription terminator-like sequence was found 25 bp downstream of the termination codon. The amino acid sequences of beta-GalI and beta-GalIII are homologous to those found in the LacZ and the LacG families, respectively. The acid-base, nucleophilic, and substrate recognition sites conserved in the LacZ family were found in beta-GalI, and a possible acid-base site proposed for the LacG family was located in beta-GalIII, which featured a glutamate at residue 160. The coding regions of the beta-galI and beta-galIII genes were each cloned downstream of a T7 promoter for overexpression in Escherichia coli. The molecular masses of the overexpressed proteins, as estimated by polyacrylamide gel electrophoresis on sodium dodecyl sulfate-polyacrylamide gels, agree with their predicted molecular weights. beta-GalI and beta-GalIII were specific for beta-D-anomer-linked galactoside substrates. Both are more active in response to ONPG (o-nitrophenyl-beta-D-galactopyranoside) than in response to lactose, particularly beta-GalIII. The galacto-oligosaccharide yield in the reaction catalyzed by beta-GalI at 37 degrees C in 20% (wt/vol) lactose solution was 130 mg/ml, which is more than six times higher than the maximum yield obtained with beta-GalIII. The structure of the major trisaccharide produced by beta-GalI catalysis was characterized as O-beta-D-galactopyranosyl-(1-3)-O-beta-D-galactopyranosyl-(1-4)-D-glucopyranose (3'-galactosyl-lactose).
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".