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PubMed1995

Synthesis and secretion of caseins by the mouse mammary gland: production and characterization of new polyclonal antibodies.

Polyclonal antibodies to mouse alpha- and beta/gamma-caseins were raised in rabbits. These antibodies display tissue- and species specificity as shown by immunoblotting. Immunohistochemical analyses demonstrate that both alpha- and beta/gamma-caseins were synthesized and secreted from virtually all lactating mammary epithelial cells, in a pattern very similar to that of the mouse alpha-lactalbumin. Residual amounts of caseins were located also in the apical surface of epithelial cells surrounding the ducal lumen of virgin mammary gland sections. In contrast to the significant level of gamma-casein in the milk, the amount of this protein compared to alpha- or beta-caseins was extremely low in medium conditioned for 24 h by mammary explants of mid-pregnant mice immediately after explantation or after 4 days.

Animals↗
PubMed1978

[The particular solution state of processed casein (author's transl)].

Processed casein manufactured with melting salts has properties which are not consisted with a solution of casein in water. The specific partial volume of the water VW = 1.061 cm3/g is clearly increased compared with pure water (VW = 1.00177 cm3/g). The activity of the water aW is greater than 1 instead of less than 1. The irregularities are explained by a solution state which is comparable to an inverted solution. That means that by melting salts in the melt water is absorbed from casein. Water now becomes the solute, whose cohesive forces are decreased. The result is an increase of the partial volume and a higher water activity.

Caseins↗
PubMed1993

The effect of casein phosphopeptides on calcium utilization in young ovariectomized rats.

The effect of casein phosphopeptides (CPPs) on Ca utilization in ovariectomized (OVX) rats was studied. A mixture of CPPs corresponding to the amino acid sequences 1-25 and 1-28 in the beta-casein was isolated from the tryptic digest of beta-casein (beta CPP). After being fed a low Ca diet for 30 days, OVX rats were fed experimental diets of which the Ca level was 0.1%, 0.3% or 0.5% with or without 0.15% beta CPP for 28 days. During days 1-3 of the Ca refeeding period, rats fed beta CPP with 0.5% Ca showed a higher Ca absorption than control rats not supplemented with beta CPP. During days 7-9 and 26-28, there were no significant differences in Ca and P balances between the beta CPP group and the control group for each dietary Ca level. Femoral Ca and P contents from rats fed beta CPP tended to be higher than those from control rats. These results suggest that beta CPP supplementation could have an effect on Ca absorption at a certain degree of Ca deficiency.

Absorption↗
PubMed1988

Casein, a prohormone with an immunomodulating role for the newborn?

Maternal colostrum and milk, the earliest food of the newborn, should not only be considered as supplying nutrients, but also as agents providing protection against aggressions from the new environment. Indeed by enzymatic digestion of the main milk proteins, the caseins, biologically active peptides are released; they may be implicated in the stimulation of the newborn's immune system. From this point of view a 'strategic active zone' has been characterized in beta-casein. A possible role of casein as a 'prohormone' for the newborn is suggested.

Caseins↗
PubMed1996

Mammary gland-specific hypomethylation of Hpa II sites flanking the bovine alpha S1-casein gene.

In the lactating cow, mammary gland-specific hypomethylation occurs at two Hpa II sites in the 5'-flanking region of the alpha S1-casein gene, and one in the 3'-region. These sites, A, B and C, are at nucleotide position -1388, -774 and +18034, respectively, relative to the major transcription start site. Site B was hypomethylated when the alpha S1-casein gene was expressed, and methylated when not expressed. In transgenic mice containing the bovine alpha S1-casein 5' and 3' regulatory elements fused to the human lactoferrin (hLF) cDNA, in some cases similar methylation patterns of sites A and B, as compared to the situation in the cow, were observed. In five mouse lines (out of the seven analysed) expressing the transgene in the milk, site B was hypomethylated in the mammary gland, while it was methylated in liver. In the two other mouse lines, no correlation was found between transgene expression and mammary gland-specific hypomethylation of site B. One of the five mouse lines with transgene expression and showing mammary-gland-specific hypomethylation of site B was studied in detail. In this mouse line, induction of transgene expression preceded hypomethylation of site B.

Animals↗
PubMed1985

Influence of dietary casein and soy protein isolate on intestinal cholesterol and bile acid concentration.

This study reports quantitative and qualitative differences in intestinal bile acids and cholesterol in miniature pigs following dietary casein or soy protein isolate. The total amount of bile acids in the small intestine was significantly higher when soy protein isolate was fed in comparison to casein. The values were (mean +/- SEM) 4.51 +/- 0.39 mmol and 2.43 +/- 0.08 mmol, respectively, when the proteins were given as the sole component of the diet. When the proteins were given as part of a semi-purified diet, these values were 6.44 +/- 1.04 mmol and 3.95 +/- 0.39 mmol, respectively. Hyocholic acid amounted to 39.6%, hyodeoxycholic acid to 31%, and chenodeoxycholic acid to 27.6% of total bile acids in the small intestine when casein was fed. The soy-fed animals tended to have more secondary bile acids. The total small bowel chymus content, on a wet weight basis, was 63% higher in the soy group. In all experimental conditions studied, there was a close correlation between small bowel chyme content and bile acid content. The distribution of bile acids in the small intestine showed that the soy fed animals tended to have more bile acids in the distal parts of the jejunum. The intestinal cholesterol contents were not significantly different between dietary groups.

Animals↗
PubMed1992

Adsorption of phenylalanine from casein hydrolysates.

The specific diet therapy for phenylalaninemies requires special hydrolysates of proteins where phenylalanine content is reduced to approx 0.53% of the amino acids present. In previous work, Amberlite XAD-4 resin was used to retain phenylalanine from an acid hydrolysate of casein. It was also observed that the adsorption isotherm of phenylalanine on the resin showed a convex pattern that allowed a frontal chromatography. In the present study, this technique was improved, aiming at the processing of larger hydrolysates volumes. This was achieved with the use of two sequential columns (50 x 1 cm), each containing 34 cm3 of the resin, and joined through a 1-cm long tygon, tube 1 mm diameter. This system was used to process 100 mL of casein acid hydrolysate containing 12 g of free amino acid and allowed the reduction of phenylalanine content from 4.39 to 0.14% of the total amino acids present, within 1 h. It was also observed that this technique could not be directly applied to enzymatic hydrolysates of casein unless they were especially produced for this purpose, which means that in this kind of hydrolysate, phenylalanine should be free or linked in small adsorptive peptides.

Adsorption↗
PubMed1998

Inhibitory effects of 1,25(OH)2D3 on membrane-associated and cytosolic casein kinase activity in MC3T3-E1 osteoblast-like cells.

The secretion of phosphorylated matrix proteins is high in osteoblasts. Phosphorylation of these proteins may be catalyzed by casein kinases (CK), and CK may play an important role in the site of bone mineralization. In this study, we examined the effects of 1, 25(OH)2D3 on CK activities in MC3T3-E1 osteoblast-like cells. Different concentrations (ranging from 10(-7) to 10(-11)M) of 1, 25(OH)2D3 were included in a culture medium. After incubation for various lengths of time, MC3T3-E1 cells were homogenized and segregated into cytosolic (c) and microsomal (m) fractions. To measure CK activity, each fraction was used as an enzyme source to phosphorylate casein. MC3T3-E1 cells showed the highest cCK activity after incubation for 21 days, and showed the highest mCK activity after incubation for 14 days. 1,25(OH)2D3 inhibited mCK activity at the early stage of culture, but inhibited cCK activity at the late stage of culture. In contrast, 1,25(OH)2D3 had a slight stimulatory effect on CK activity in the culture medium of MC3T3-E1 cells. Our data suggest that cCK and mCK may play different roles in the function of osteoblasts, and 1,25(OH)2D3 regulates intracellular and extracellular casein kinase activities related to the function of osteoblasts.

3T3 Cells↗
PubMed2006

Size distribution of pressure-decomposed casein micelles studied by dynamic light scattering and AFM.

Reversible and irreversible states of pressure-dissociated casein micelles were studied by in situ light scattering techniques and ex situ atomic force microscopy. AFM experiments performed at ambient pressure reveal heterogeneities across the micelle, suggesting a sub-structure on a 20 nm scale. At pressures between 50 and 250 MPa, the native micelles disintegrate into small fragments on the scale of the observed sub-structure. At pressures above 300 MPa the micelles fully decompose into their monomeric constituents. After pressure release two discrete populations of casein aggregates are observed, depending on the applied initial pressure: Between 160 and 240 MPa stable micelles with diameters near 100 nm without detectable sub-structures are formed. Casein micelles exposed to pressures above 280 MPa re-associate at ambient pressure yielding mini-micelles with diameters near 25 nm. The implications concerning structural models are discussed.

Biophysical Phenomena↗
PubMed2000

Recombinant expression analysis of natural and synthetic bovine alpha-casein in Escherichia coli.

As a prelude to developing a yeast-based fermentation process for the production of phenylalanine-free alpha-casein as a foodstuff for patients suffering from phenylketonuria, we cloned the gene encoding bovine alpha-casein. We synthesised a modified gene sequence encoding the same, but devoid of phenylalanine codons and with a codon bias similar to that of naturally occurring highly expressed genes in Saccharomyces cerevisiae. The results show that both gene sequences are readily expressed in Escherichia coli when cloned in an E. coli bacteriophage T7 promoter-driven plasmid vector. In this host, the natural and synthetic casein proteins were produced at levels equating to 18.0% and 7.6% of the cell's soluble protein, respectively.

Amino Acid Sequence↗
PubMed2002

Regulation of glycolysis by casein kinase I (Rag8p) in Kluyveromyces lactis involves a DNA-binding protein, Sck1p, a homologue of Sgc1p of Saccharomyces cerevisiae.

The casein kinase I (Rag8p) of Kluyveromyces lactis has previously been shown to regulate the transcription of the low-affinity glucose transporter gene RAG1. To study this regulation, we have isolated multicopy suppressors of the rag8 mutation. One of them, SCK1 (suppressor of casein kinase), was characterised. The predicted product of the gene has a DNA-binding signature of the basic-helix-loop-helix type. It has an overall identity of 38% with Sgc1p (Tye7p) of Saccharomyces cerevisiae. The sck1 null mutant exhibited a Rag- phenotype (which indicates a reduced flux of glycolysis) that can be complemented by the SGC1 gene of S. cerevisiae. The level of transcription of several glycolytic genes, including RAG1, was reduced about twofold in glucose media in the sck1 null mutant. Moreover, in a rag8 mutant, the expression of SCK1 was strongly affected. Altogether, the results suggest that the regulation of glycolysis by casein kinase I involves, at least in part, Sck1p in K. lactis.

Amino Acid Sequence↗
PubMed2004

Effects of a tryptic hydrolysate from bovine milk alphaS1-casein on hemodynamic responses in healthy human volunteers facing successive mental and physical stress situations.

BACKGROUND: Preclinical results in rats have demonstrated anxiolytic-like effects of a tryptic bovine alphaS1-casein hydrolysate. AIM OF THE STUDY: We investigated the putative effects of this tryptic hydrolysate on systolic (SBP), diastolic (DBP) blood pressures, heart rate (HR) values and plasma cortisol concentrations (CC) in human healthy volunteers facing successive stress situations. METHODS: The subjects were (double blind) randomly allocated to ingest three times, 12 hours apart, two capsules containing either 200 mg of alphaS1-casein hydrolysate (TS) or bovine skimmed milk powder as a placebo (CS). On the morning of the test day, a first blood sample for baseline measurement of CC was taken before the subjects were submitted to the Stroop test (ST) and, after a 30-min rest, to a Cold Pressor test (CPT). SBP, DBP, and HR were continuously recorded for 5 min before the ST and during each stress situation. A second blood sample was taken 15 min after the end of the CPT condition. RESULTS: ST and ST + CPT combined test situations increased SBP, DBP and HR. The significant "Treatment x SBP" and "Treatment x DBP" interactions indicated the lower percentage changes in SBP and DBP of the TS. In addition, the results showed a significant decrease of the CC in the TS but not in the CS throughout the ST + CPT combined stress tests. HR remained stable in TS between the initial rest period and the CPT unlike what happened in CS. CONCLUSION: On the basis of blood pressure and cortisol changes, these results suggest an antistress profile of this alphaS1-casein hydrolysate in human subjects.

Analysis of Variance↗
PubMed2006

Casein kinase-1 isoforms differentially associate with neurofibrillary and granulovacuolar degeneration lesions.

Alzheimer's Disease (AD) is characterized by the appearance of neurofibrillary and granulovacuolar lesions in the brains of affected individuals. The former is composed of hyperphosphorylated aggregates of the microtubule-associated protein tau. The latter is poorly characterized but reacts strongly with anti-phosphoepitope antibodies indicating that it too accumulates phosphoproteins. Both lesions react strongly with antibodies directed against members of the casein kinase-1 family of phosphotransferases, a group of closely related protein kinases that frequently function in tandem with the ubiquitin modification system. To determine whether individual members of the casein kinase-1 family differentially associate with AD lesions, hippocampal sections isolated from late stage cases of AD were subjected to double-label fluorescence immunohistochemistry using a panel of selective anti-casein kinase 1 antibodies and small-molecule fluorochromes thioflavin S and thiazin red. The resultant colocalization patterns revealed that the alpha CK1 isoform strongly correlated with thioflavin S and thiazin red fluorescence, indicating that it preferentially associated with neurofibrillary lesions. In contrast, the delta isoform staining pattern was dominated by colocalization with granulovacuolar degeneration bodies. These findings suggest that granulovacuolar and neurofibrillary lesions occupy separate populations of neurons, and implicate CK1 isoforms in the generation of lesion-associated phosphoepitopes. They also suggest a nexus between the phosphorylation and ubiquitination modifications found in both lesions.

Aged, 80 and over↗
PubMed2002

Pseudophosphorylated prolactin (S179D PRL) inhibits growth and promotes beta-casein gene expression in the rat mammary gland.

We have investigated the individual roles of unmodified prolactin (U-PRL) and a mimic of phosphorylated PRL (S179D PRL) in mammary development. Recombinant versions of the PRLs were delivered to rats throughout pregnancy at a rate of 6 microg/24 h per rat and to non-pregnant females at a rate of 24 microg/24 h per rat. Measurement of progesterone, corticosterone, and estradiol showed no effect of the administered PRLs on the levels of these other mammotropic hormones. Histological and morphometric analysis showed U-PRL to cause mammary growth, whereas S179D PRL inhibited growth. Molecular analysis demonstrated decreased beta-casein expression in the mammary glands of the U-PRL-treated animals at term and increased beta-casein expression in the mammary glands of the S179D PRL-treated animals. Superior beta-casein gene expression in response to S179D PRL versus U-PRL was confirmed in HC11 cells. We conclude that U-PRL is important for growth, whereas S179D PRL promotes at least one measure of differentiated function in the mammary gland.

Amino Acid Substitution↗
PubMed1984

Fluorescein isothiocyanate-labeled casein assay for proteolytic enzymes.

A simple inexpensive sensitive protease assay was developed using soluble fluorescein isothiocyanate (FITC)-labeled casein. Casein was reacted with FITC to form the fluorescein thiocarbamoyl derivative. This substrate is cleaved by trypsin, chymotrypsin, elastase, subtilisin, and thermolysin in a linear time-dependent manner. These enzymes can be measured in the nanogram and subnanogram range using this assay. The assay is reproducible, has a low blank, and uses casein, which resembles natural substrates of most proteases.

Animals↗
PubMed1990

Enhanced removal of detergent and recovery of enzymatic activity following sodium dodecyl sulfate-polyacrylamide gel electrophoresis: use of casein in gel wash buffer.

The inclusion of 1% casein or bovine serum albumin in buffer used to reactivate enzymes subjected to sodium dodecyl sulfate (SDS)-polyacrylamide electrophoresis resulted in accelerated removal of SDS and restoration of nuclease and beta-galactosidase enzyme activities. Nuclease and beta-galactosidase activities which are absent from gels after longer wash procedures are detectable with this technique. Enzyme activity in gels prepared with SDS which contained inhibitory contaminants was partially restored by the casein wash procedure. The threshold of detection of two-dimensionally separated deoxyribonuclease I using the casein wash procedure was 1 picogram.

Autoradiography↗
PubMed1983

Identification of calcium-independent myosin kinase with casein kinase II.

A crude myosin fraction from bovine brain has been found to contain a Ca2+-independent myosin kinase that catalyzes the phosphorylation of 20,000-Da light chain of gizzard myosin. The myosin kinase has been separated from the myosin by Sepharose CL-4B gel filtration and purified further by chromatography on phosphocellulose, Sephacryl S-300, and hydroxylapatite. The myosin kinase was found to copurify with casein kinase II and show the same substrate specificity with the casein kinase. These results indicate that the myosin kinase is identical to casein kinase II. The purified myosin kinase catalyzed the preferential phosphorylation of the threonyl residues of 20,000-Da light chains of gizzard and brain myosins. The 17,000-Da light chains of these myosins and the mixed light chains of skeletal and cardiac muscle myosins were not phosphorylated by the enzyme to an appreciable extent.

Amino Acids↗
PubMed1984

The phosphorylation site for casein kinase II on 20,000-Da light chain of gizzard myosin.

The 20-kDa light chain isolated from gizzard myosin has recently been reported to be phosphorylated by casein kinase II at a site distinct from that phosphorylated by Ca2+- and calmodulin-dependent myosin light-chain kinase. In the present study, the site phosphorylated by casein kinase II has been analyzed through procedures including tryptic digestion of the radioactively phosphorylated light chain and CNBr cleavage of the purified tryptic phosphopeptide, followed by amino acid analysis of these phosphopeptides. Comparison of the amino acid compositions of these peptides with the previously reported sequence has indicated that the phosphorylation site is threonine-134 of the light chain. The significance of the phosphorylation of the light chain by casein kinase II, as well as the substrate specificity of the protein kinase, is discussed on the basis of the result.

Amino Acids↗