Effect of genetic variants on hydrolysis of bovine k-casein by chymosin and pepsin
Bibliographic record
Abstract
Caseins are present in milk in the form of large spherical complexes called micelles that are stabilized by kappa-casein found on the surface. This stabilizing effect is lost when milk clotting enzymes hydrolyze kappa-casein thereby initiating the coagulation process. The objective of this study was to analyze the effect of kappa-casein polymorphism upon hydrolysis by proteases. The A and B forms are the most common genetic variants of kappa-casein in Canadian Holstein dairy herds, representing three phenotypes AA, AB and BB. Whole casein from Holstein milk samples was fractionated into its four major components by ion-exchange chromatography using Express Ion Exchanger Q Anion Exchanger and Macro-Prep High Q Anion Exchange Support columns. The kappa-casein fraction was isolated, dialyzed, and assessed for its phenotype and purity by PAGE. The pure forms of the three different phenotypes of kappa-casein (AA, AB, BB) at a final concentration of 0.5% were then hydrolyzed by calf chymosin (1:500) and porcine pepsin (1:1000) at a pH of 5.8 at 37°C. Aliquots were collected at 0, 5, 15, 30, 60 and 90 min and the reaction stopped by using 24% NH4OH. The rate of hydrolysis of the three phenotypes was analyzed by comparing the disappearance of the substrate with time from the RP-HPLC chromatograms using Waters MAXIMA software. SDS-PAGE was used to calculate the approximate molecular weight of the hydrolytic products. Analysis of the hydrolysate profiles indicated that there was significant difference (P < 0.05) in the rate of hydrolysis between the phenotypes. Under the present conditions at a pH of 5.8, the AA phenotype showed a significantly slower rate of hydrolysis by both chymosin and pepsin, than the other two phenotypes. There was no significant difference in the rate of hydrolysis between the phenotypes AB and BB during chymosin hydrolysis. The BB phenotype is hydrolyzed more extensively and the AB phenotype is intermediate between the two variants in the p
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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) | 0.000 | 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 | 0.000 |
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".