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PubMed2005

IgE-mediated rat mast cell triggering with tryptic and synthetic peptides of bovine beta-lactoglobulin.

BACKGROUND: Immunoglobulin E (IgE) epitopes of beta-lactoglubulin (betaLG) have been identified by ELISA inhibition methods using sera from allergic patients. However, the functional capacity of these epitopes to stimulate mast cells is unknown. It is the goal of the present study to identify bivalent IgE epitopes of betaLG able to trigger target mast cells. METHODS: Peptides were obtained either by purification from tryptic hydrolysates of betaLG or by synthesis. They were examined for their triggering activity in vitro on peritoneal 3H-serotonin-labeled rat mast cells passively sensitized with IgE anti-betaLG antibodies. In vivo, rats immunized with betaLG were administered peptides by gavage for intestinal rat mast cell protease II release. RESULTS: Compared with intact betaLG, purified or synthetic tryptic-like betaLG peptides have a sharply decreased allergenicity. Peptide 149-162 retains the highest bivalent IgE epitope-mediated triggering capacity. CONCLUSION: A functional bivalent IgE epitope was identified at the C terminal end of betaLG.

Amino Acid Sequence↗
PubMed1995

Prediction of milk yields from serum beta-lactoglobulin concentrations in pregnant heifers.

The serum concentration of beta-LG at wk 26 of pregnancy was determined in Holstein heifers of known genetic merit to evaluate use of a single blood sample as an index to predict their subsequent milk yield. Concentrations of beta-LG varied widely (16 to 1200 ng/ml) in the serum of the heifers at this stage of pregnancy. Subsequent measures of lactation performance showed that heifers with high beta-LG concentrations in pregnancy produced more milk than those with low beta-LG in serum. Previous studies have shown that the concentration of beta-LG in serum shows a log-linear increase during pregnancy, which is consistent with correlation to the growth of the mammary parenchyma. Therefore, the logarithm beta-LG concentration was used as the index in this study. The correlations of this index were .46, .54, and .48 for first lactation 305-d yields of milk, fat, and protein, respectively. The results suggest that serum concentrations of beta-LG estimated from a single blood sample at this stage of pregnancy can be used to predict milk yield. Analysis showed that an explanation of future milk yield was significantly improved by use of serum beta-LG and parent average. Serum beta-LG can be used as a physiological marker to prescreen heifers for lactation potential.

Animals↗
PubMed1995

Susceptibility of beta-lactoglobulin and sodium caseinate to proteolysis by pepsin and trypsin.

The susceptibility of beta-LG and sodium caseinate to proteolysis by pepsin and trypsin was investigated using SDS or urea-PAGE. The effects were studied of heat, urea, and 2-mercaptoethanol on proteolysis. Native beta-LG was resistant to hydrolysis by pepsin or trypsin because of its compact globular structure. Heat treatment of beta-LG solutions at 90 to 100 degrees C for 5 or 10 min caused changes in the structure or conformation of the protein that rendered it accessible to pepsin and enhanced the extent of proteolysis by trypsin. The susceptibility of beta-LG to proteolysis by pepsin was markedly increased in the presence of urea (3 to 6 M), and the effect was reversible after removal of urea by dialysis. Proteolysis by trypsin was also increased by the presence of 2% 2-mercaptoethanol. Sodium caseinate was very accessible to pepsin without pretreatment and was extensively hydrolyzed at pH 1 to 5 in the presence of 5 M urea (which prevented the protein from precipitation in the isoelectric region); optimal pH was about 2. The activity of pepsin on sodium caseinate at pH 2 was not significantly affected by urea concentration up to about 8 M. The results indicated that the changes in conformation and structure of beta-LG that were induced by heating, reduction, or urea rendered the protein susceptible to peptic hydrolysis.

Animals↗
PubMed1995

Application of capillary electrophoresis in the identification of phenotypes containing the beta-lactoglobulin C variant.

A method for the separation of the beta-LG variants A, B, and C was developed using free zone capillary electrophoresis. A separation buffer consisting of 50 mM 2-(N-morpholino)ethane sulfonic acid (pH 8.0) and polyoxyethylene (20)-sorbitan monolaurate was used for the separation. Milk samples from 424 Jersey cows were phenotyped using this method, and the gene frequencies for beta-LG A, B, and C were .41, .53, and .06, respectively. These frequencies were different from those found in studies of Jersey populations in other countries, where the beta-LG B allele had a significantly higher frequency, and the beta-LG A allele a significantly lower frequency, than those of this present study. The frequency of the beta-LG C allele was intermediate to those of other studies. The concentration of beta-LG in the milk was different among the beta-LG phenotypes and was, from greatest to least: AA, AB, AC, BB, and BC.

Animals↗
PubMed1997

Marked effect of beta-lactoglobulin polymorphism on the ratio of casein to total protein in milk.

The relationship between genetic variants for milk protein and the composition of milk was analyzed on 4475 repeated milk samples from individual cows; 371 dairy cows of the Swedish Red and White breed and 204 cows of the Swedish Holstein breed were used. The registrations included percentages of casein, protein, fat, and lactose in combination with milk yield and SCC. The genotype of individual cows for alpha(s1)-CN, beta-CN, kappa-CN, and beta-LG was determined by alkaline and acidic PAGE. A mixed animal model was used for the analysis; beta-LG and aggregate casein genotypes were included simultaneously as separate fixed effects in the statistical model. The results suggest a positive additive effect of the beta-LG B allele on casein content and on the ratio of casein to total protein. For the latter trait, the beta-LG genotype accounted for a relatively large part of the phenotypic variance, corresponding to a reduction in residual variance of 11% when included in the model. The corresponding value for casein content was 0.5%. The lack of unfavorable associations between milk protein variants and the traits included in this study makes the beta-LG gene an obvious candidate when the breeding objective is improved conversion of milk protein into cheese.

Animals↗