Search

Chinese Royal cheese, an ancient and attractive dairy product now in China, is made from milk coagulated with glutinous rice wine. In this paper, it was mainly studied on the proteolytic property toward proteins of bovine milk including caseins (CN) and whey proteins and the cleavage bond on the κ -CN of rennet-like enzyme purified from glutinous rice wine by ion-exchange chromatography. Compared with whey protein, the rennet-like protease has substrate specificity toward CN but with different hydrolysis degrees among κ -, α -, and β -CN, and the α -CN was almost completely degraded, whereas κ - and β -CN partly showed hydrolysis in 12h. The analysis for enzyme digestion by electrospray tandem mass spectrometry, Q-TOF2, and matrix-assisted laser desorption-ionization time-of-flight mass spectrometry revealed that the cleavage of protease from glutinous rice wine on κ -CN mainly happens at the Thr 94 -Met 95 bond, which is different from the most chymosin-sensitive bond, Phe 105 -Met 106 .

The Na+-dependent glucose cotransporters (SGLT) are a family of glucose transporters that mediate an active, sodium-linked transport process against an electrochemical gradient. The SGLT are known to play important roles in absorption of dietary D-glucose and D-galactose from the intestinal lumen and in the reabsorption of D-glucose from the glomerular filtrate in kidney. To study the role and regulation of SGLT in tissues of lactating cows, we cloned and sequenced the full-length cDNA of bovine SGLT1 and SGLT5. Open reading frame analysis predicted that bovine SGLT1 is composed of 664 amino acids with a molecular weight of approximately 73 kDa, and SGLT5 is composed of 597 amino acids with a molecular weight of approximately 65 kDa. The deduced amino acid sequence of bovine SGLT1 is 48% identical and 66% conserved relative to that of bSGLT5. The amino acid sequence of bovine SGLT1 is 97, 88, 87, 86, 85, and 84% identical to sheep, mouse, rat, horse, human, and rabbit SGLT1, respectively. In contrast, the amino acid sequence of bSGLT5 is relatively divergent among species, being 85, 64, and 48% identical to rabbit, human, and rat SGLT5, respectively. Bovine SGLT retain the characteristic structural features of SGLT1 proteins described in other species, including membrane-spanning helices and glucose transporter motifs. The major in vitro transcription and translation product of bovine SGLT1 cDNA migrated at an apparent molecular weight of 52 kDa. In the presence of canine microsomal membranes, the translation product increased to 53 kDa, suggesting glycosylation. The SGLT1 mRNA was most abundant in bovine intestine, at intermediate levels in bovine kidney, and at lower levels in bovine mammary gland, liver, and lung. No SGLT1 mRNA was detected in bovine spleen, skeletal muscle, or testes. Expression of SGLT5 mRNA was found predominantly in bovine kidney, only at very low levels in bovine testes, skeletal muscle, and spleen, and was essentially undetectable in bovine mammary gland, liver, lung, and small intestine. Abundance of SGLT1 mRNA in bovine mammary gland increased more than 4-fold during late pregnancy and early lactation. The sequence and expression data reported in this paper lay the groundwork for future studies aimed at unraveling the functional roles of SGLT in supporting milk production and maintaining glucose homeostasis during lactation.

Many angiotensin converting enzyme inhibitory peptides (ACEIP) have been identified in recent years. Among all the literatures available thus far, almost all the ACEIP were obtained by means of enzymatic hydrolysis. However, little information was available on antihypertensive peptides obtained by DNA recombination technology. In the present paper, our aims were 1) to establish a new method to produce antihypertensive peptides (AHP), and 2) to study the expression profiles of different host strains ( Escherichia coli JM109 and DH5 α ). To achieve these objectives, a DNA fragment encoding the published ACEIP, identified as FFVAPFPEVFGK (known as CEI 12 ) was synthesized, ligated with the expression vector, pQE16, and transformed into E. coli JM109 and DH5 α . SDS-PAGE analysis and Western-blotting detection demonstrated that the peptide CEI 12 (fused with dihydrofolate reductase [DHFR]) was specifically expressed only in E. coli JM109 with IPTG induction. The expression profiles of the AHP CEI 12 at different IPTG concentrations and different inducing times demonstrated no significant differences by SDS-PAGE analysis. The expression level of CEI 12 (fused with DHFR) was about 500 μ g/L culture.

alpha(S2)-Casein (alpha(S2)-CN) comprises up to 10% of the casein fraction in bovine milk. The role of alpha(S2)-CN in casein micelles has not been studied in detail in part because of a lack of structural information on the molecule. Interest in the utilization of this molecule in dairy products and nutrition has been renewed by work in 3 areas: biological activity via potentially biologically active peptides, functionality in cheeses and products, and nutrition in terms of calcium uptake. To help clarify the behavior of alpha(S2)-CN in its structure-function relationships in milk and its possible applications in dairy products, this paper reviews the chemistry of the protein and presents a working 3-dimensional molecular model for this casein. The model was produced by threading the backbone sequence of the protein onto a homologous protein: chloride intracellular channel protein-4. Overall, the model is in good agreement with experimental data for the protein, although the amount of helix may be over-predicted. The model, however, offers a unique view of the highly positive C-terminal portion of the molecule as a surface-accessible area. This region may be the site for interactions with kappa-carrageenan, phosphate, and other anions. In addition, most of the physiologically active peptides isolated from alpha(S2)-CN occur in this region. This structure should be viewed as a working model that can be changed as more precise experimental data are obtained.

The Na+-dependent glucose cotransporters (SGLT) are a family of glucose transporters that mediate an active, sodium-linked transport process against an electrochemical gradient. The SGLT are known to play important roles in absorption of dietary D-glucose and D-galactose from the intestinal lumen and in the reabsorption of D-glucose from the glomerular filtrate in kidney. To study the role and regulation of SGLT in tissues of lactating cows, we cloned and sequenced the full-length cDNA of bovine SGLT1 and SGLT5. Open reading frame analysis predicted that bovine SGLT1 is composed of 664 amino acids with a molecular weight of approximately 73 kDa, and SGLT5 is composed of 597 amino acids with a molecular weight of approximately 65 kDa. The deduced amino acid sequence of bovine SGLT1 is 48% identical and 66% conserved relative to that of bSGLT5. The amino acid sequence of bovine SGLT1 is 97, 88, 87, 86, 85, and 84% identical to sheep, mouse, rat, horse, human, and rabbit SGLT1, respectively. In contrast, the amino acid sequence of bSGLT5 is relatively divergent among species, being 85, 64, and 48% identical to rabbit, human, and rat SGLT5, respectively. Bovine SGLT retain the characteristic structural features of SGLT1 proteins described in other species, including membrane-spanning helices and glucose transporter motifs. The major in vitro transcription and translation product of bovine SGLT1 cDNA migrated at an apparent molecular weight of 52 kDa. In the presence of canine microsomal membranes, the translation product increased to 53 kDa, suggesting glycosylation. The SGLT1 mRNA was most abundant in bovine intestine, at intermediate levels in bovine kidney, and at lower levels in bovine mammary gland, liver, and lung. No SGLT1 mRNA was detected in bovine spleen, skeletal muscle, or testes. Expression of SGLT5 mRNA was found predominantly in bovine kidney, only at very low levels in bovine testes, skeletal muscle, and spleen, and was essentially undetectable in bovine mammary gland, liver, lung, and small intestine. Abundance of SGLT1 mRNA in bovine mammary gland increased more than 4-fold during late pregnancy and early lactation. The sequence and expression data reported in this paper lay the groundwork for future studies aimed at unraveling the functional roles of SGLT in supporting milk production and maintaining glucose homeostasis during lactation.

This paper describes the specific activities for proline iminopeptidases, x-prolyl dipeptidyl peptidase and post proline endopeptidase, from each of two subspecies of Lactobacillus casei grown in MRS broth and whey media at 37°C, pH 6.0. The histochemical PAGE of soluble extracts from one subspecies ( Lactobacillus casei ssp. casei LLG) indicated that the two enzyme activities were due to distinct proteins. Except for a slight increase in x-prolyl dipeptidyl peptidase activity, the activities of proline imino- and endopeptidases of cells grown in whey medium did not vary markedly from those of cells grown in MRS broth. The effect of inhibitor agents and pH on the activities of proline iminopeptidase and x-prolyl dipeptidyl peptidase were investigated. The temperature optima and storage stability under different conditions were also studied for these activities.

The present paper is devoted to the study of short peptides derived from milk proteins with physiological activities. Some of them behaved as opioids, enzyme inhibitors that convert angiotensin I, peptides that enhance calcium absorption, antiaggregating and antithrombotic peptides, and immunomodulating peptides. Some possessed several physiological properties, such as the C-terminal part of bovine alpha s1-casein. A strategic zone, containing immunostimulating and opioid peptides, could be located in cow and human beta-caseins. Few of these peptides or precursor peptides have so far been characterized in vivo in blood or brain after ingestion of milk. If, in the future, some of the active peptides cannot be characterized in vivo, they can all nevertheless be synthesized and used either as food additives or in pharmacology.

The structure and stability of casein micelles are determined in large measure by the amino acid sequences of the constituent alphas1-, beta-, and kappa- caseins. In this paper we review, and attempt to connect with sequence data where possible: (1) molecular weight, structure, and dissociation of casein micelles; (2) physical characteristics of monomeric caseins, especially the distrubition of charged and hydrophobic residues and the possible occurrence of helical regions; and (3) forces involved in association of monomers.