Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.7 (plasmin)
 9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of heating on plasmin activity in various media, including phosphate buffer pH 7.0, skim milk, blood plasma, solutions of casein and solutions of whey proteins were investigated. Plots of log residual activity v. heating time were linear at all temperatures from 63 to 143 degrees C. In buffer solutions the presence of casein led to substantial substrate protection, the Arrhenius plots being linear both in the presence and absence of casein. The activation energy, Ea, for the inactivation reaction, was 62.4 kJ/mol in buffer alone and 58.4 kJ/mol with casein present at 25 mg/ml. In skim milk, despite the presence of casein at a similar concentration, plasmin was no more stable to heat than in buffer alone, and a curved Arrhenius plot was obtained indicating a more complex inactivation mechanism. Heating in the presence of proteins having free -SH groups accelerated the inactivation of plasmin. The role of -SH groups was confirmed by experiments with added alpha-lactalbumin, in which no free -SH groups occur, and reduced carboxymethylated beta-lactoglobulin, both of which were without effect. In blood plasma, plasmin was less stable to heat than in buffer (pH 7.0) or in skim milk. Plasminogen behaved very similarly to plasmin either when activated to plasmin with urokinase before heating or when activated afterwards. A hypothesis is presented to describe the heat inactivation and denaturation of plasmin. Technologically important findings are that in skim milk plasmin was largely unaffected by pasteurization conditions and 30-40% of its activity remained even after ultra high temperature processing conditions.
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PMID:Heat stability of plasmin (milk proteinase) and plasminogen. 294 65

The major proteins in milks from bovine, caprine, porcine, and murine animals and from humans were compared using a two-dimensional analysis method. In the first dimension, proteins were separated by their isoelectric points using preparative isoelectric focusing in pH gradient of 3 to 10. Twenty fractions from each sample were then analyzed by urea-PAGE and SDS-PAGE. Two-dimensional gels showed characteristic patterns for each milk. Major bovine milk proteins were identified and used as reference for proteins of other mammals. Additionally, some peptides resulting from plasmin hydrolysis were characterized. Caprine milk proteins showed a pattern similar to that of bovine milk except for the absence of alpha s1-caseins. alpha-Lactalbumin of bovine and caprine milks resolved as two bands in an immunoblot using bovine alpha-lactalbumin antibody. Each band corresponded to normal and glycosylated alpha-lactalbumin. Human, porcine, and murine milk proteins were totally different from those of ruminant milks on the two-dimensional gels. Two-dimensional analysis using preparative isoelectric focusing, followed by PAGE, was a useful method to compare major milk proteins in several mammals because of the rapid simultaneous separation into 20 fractions. This fractionation allows additional analytical procedures for more efficient comparison of chemical and physical properties of the proteins.
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PMID:Comparison of milk proteins using preparative isoelectric focusing followed by polyacrylamide gel electrophoresis. 796 43

The ability of beta-lactoglobulin variants A and B, alpha-lactalbumin, and BSA to inhibit plasmin plus plasminogen activity was examined. Data showed that beta-lactoglobulin A at concentrations of .2 and 1 mg/ml inhibited plasmin plus plasminogen activity by 18 and 54%. beta-Lactoglobulin B had no effect on plasmin plus plasminogen activity. At concentrations of .2 and 1 mg/ml, BSA inhibited plasmin plus plasminogen activity by 25 and 63%. alpha-Lactalbumin at concentrations of .2 and 1 mg/ml caused 1.9 and 20% inhibition of plasmin plus plasminogen activity. These data, collectively, suggest that existing methodology for measuring plasmin activity in milk serum underestimates real plasmin activity in milk. Underestimation is more pronounced in samples with high whey protein content (late lactation milk and milk obtained from mastitic quarters). To avoid this problem, we have modified the existing methodology. Our modification allows plasmin determination without interference from whey proteins and other plasmin inhibitors that are present in the serum fraction of bovine milk.
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PMID:Enzymatic assay for the combined determination of plasmin plus plasminogen in milk: revisited. 850 18

The objective of this study was to determine the response of individual milk proteins to a reduction in amino acid (AA) availability induced by atropine and to determine whether the response was different in cows with different beta-lactoglobulin (LG) phenotypes. Six cows that were homozygous for the A variant of beta-LG and six cows that were homozygous for the B variant of beta-LG were each given a single subcutaneous injection of saline or 20 mg of atropine. In both groups of cows, atropine decreased milk yield by 30% and reduced the concentration of alpha-lactalbumin (LA) by 25 to 30% at 8 h following injection. Eight hours after atropine injection, yield of beta-LG was 41% lower than it was following saline injection, and yield of beta-casein (CN) after atropine injection declined 16% relative to saline. Concentrations of BSA and the ratio of gamma-CN to beta-CN, which reflects plasmin activity in milk, were significantly increased after administration of atropine. Although the response to atropine tended to be more pronounced in cows that were homozygous for beta-LG B, they were not significantly different from the response of cows that were homozygous for beta-LG B, they were not significantly different from the response of cows that were homozygous for beta-LG A. The differential response of individual proteins to a reduction in AA concentrations in whole blood suggested that susceptibility to restriction in substrate availability differed for individual proteins. The concentration of lactose in plasma did not change, which implied that the integrity of the mammary epithelial barrier was not compromised when AA derived from blood were diminished. The consistent concentration of lactose combined with the minimal increase in total yield of BSA in milk following atropine treatment indicated that the increased concentration in milk of proteins derived from serum was due to the concentrating effect of lower milk volume.
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PMID:Effect of atropine on milk protein yield by dairy cows with different beta-lactoglobulin phenotypes. 924 90

Several peptides were isolated from the diafiltration retentate, prepared using 10 kDa membranes, of the water-soluble extract from a commercial mature Cheddar cheese and identified by amino acid sequencing and mass spectrometry. Most of the peptides were from the N-terminal half of the beta-casein, but peptides from alpha s1- and alpha s2-caseins were also identified; the extract also contained alpha-lactalbumin. Identified peptides showed the important role played by lactococcal cell envelope proteinases in the degradation of primary proteolytic products from alpha s1- and beta-caseins, produced by chymosin and plasmin respectively. Plasmin seemed to be involved in the hydrolysation of alpha s2-casein. Several phosphopeptides were identified and the action of phosphatase on these peptides was evident.
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PMID:Isolation and identification of further peptides in the diafiltration retentate of the water-soluble fraction of Cheddar cheese. 927 58

The effects of reducing the frequency of milking of cows in late lactation on milk somatic cell count (SCC), polymorphonuclear leucocyte (PMN) content, chemical composition and proteolytic activity were investigated. Intermittent milking is frequently practised by Irish farmers in late lactation, and the objective of this study was to determine whether this procedure could be linked to altered quality of milk. Seventeen Holstein Friesian cows in late lactation (> 215 d in milk) were assigned to two treatment groups, and were either milked twice a day until drying-off (control group) or milked intermittently as the yield fell (test group). Milk composition and enzymic characteristics were measured on two occasions. At the first sampling, day 7, test cows were on once daily milking and at the second, day 15, the test cows were being milked every second day. Milk yields were significantly lower in test than control animals and decreased between days 7 and 15 in both groups. Milk SCC and PMN levels were increased on reducing milking frequency and, at day 15, the increase was not linked to decreased milk yield. Milk lactose levels were significantly decreased and pH, alpha-lactalbumin levels, plasmin activity and plasminogen activity significantly increased by reducing milking frequency. In conclusion, reduced frequency of milking in late lactation leads to the production of milk that is abnormal in character and this may be linked to reduced quality of dairy products manufactured from such milk.
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PMID:Effect of decreased milking frequency of cows in late lactation on milk somatic cell count, polymorphonuclear leucocyte numbers, composition and proteolytic activity. 971 90

The plasmin system native to bovine milk consists of the caseinolytic serine proteinase plasmin; its inactive zymogen, plasminogen; plasminogen activators; and inhibitors. Evidence in the literature indicates that whey proteins may inhibit plasmin activity, but there is very little mention of their effect on plasminogen activators. The objective of this research was to determine the effect of both unheated and heat-denatured beta-lactoglobulin (beta-LG), alpha-lactalbumin (alpha-LA), and BSA on plasminogen activators. Plasminogen activator activity was significantly stimulated by non-heat treated and denatured alpha-LA as well as by denatured beta-LG. The stimulation effect by these whey proteins was kinetically characterized, which showed that all 3 significantly increased the rate of plasminogen activation. The stimulation effect was shown to be independent of any effect of the whey proteins on plasmin activity by testing 2 different substrates, d-Val-Leu-Lys p-nitroanilide (S-2251) and Spectrozyme PL (Spec PL), in a plasmin assay. Results using S-2251 confirmed the inhibitory effect of whey proteins on plasmin observed by several researchers. However, use of SpecPL did not suggest inhibition. Ligand binding studies showed this discrepancy to be due to significant interaction between S-2251 and the whey proteins. Overall, this study indicates that whey protein incorporation into cheese may not hinder plasmin activity and may stimulate plasminogen activation. Furthermore, the results indicate the need for careful consideration of the type of synthetic substrate chosen for model work involving whey proteins and the plasmin system.
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PMID:Effects of native and denatured whey proteins on plasminogen activator activity. 1532 55

Studies of the potential of high pressure homogenisation (HPH) for the combined pasteurisation/ homogenisation of raw bovine milk were undertaken. Raw milk was preheated to 45 degrees C and HPH-treated at 150, 200 or 250 MPa; milk outlet temperature at these pressures were 67, 76.8 and 83.6 degrees C, respectively, with a holding time of approximately 20 s. Raw and commercially pasteurized and homogenized (CPH) milk samples were analysed as controls. Fat globules in HPH samples were approximately half the size of those in CPH samples, although differences were not significant (P>0.05). beta-Lactoglobulin was denatured at pressures > or =150MPa, although little denaturation of alpha-lactalbumin was observed. Numbers of psychrotrophic bacteria in raw milk were reduced by 2.73 log cycles by HPH at 150 MPa and were uncountable following HPH at 200 or 250 MPa. Mesophilic bacterial counts were reduced by 1.30, 1.83 and 3.06 log cycles by HPH at 150, 200 or 250 MPa, respectively. No viable Staphylococcus aureus nor coliform cells remained in any HPH milk samples. HPH did not affect the colour of milk and HPH samples did not cream during refrigerated storage. The activities of plasmin, alkaline phosphatase and lactoperoxidase in milk were all greatly reduced by HPH. Pseudomonas fluorescens, inoculated into milk (approximately 10(6) cfu/ml), was reduced to undetectable levels by HPH at 200MPa (milk inlet temperature, approximately 10 degrees C); however, Ps. fluorescens proteinase was quite resistant to HPH under such conditions. Overall, owing to the significant increase in temperature and the possibility of varying the holding time, there may be potential applications for HPH as a novel liquid milk processing technique, combining many advantages of conventional homogenization and pasteurization of milk in a single process.
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PMID:Potential applications of high pressure homogenisation in processing of liquid milk. 1574 28

Plasmin-mediated hydrolysis of 6 different milk protein preparations [alpha(S)-casein (alpha(S1) + alpha(S2)), beta-casein, kappa-casein, alpha-lactalbumin, beta-lactoglobulin, and lactoferrin] was found to be very dependent on photooxidation of the said proteins. Changes in plasmin proteolysis were investigated in a peptide-mapping study applying liquid chromatography-mass spectrometry. The changes were seen in the formation of peptides formed by plasmin-mediated hydrolysis after photooxidation, which was initiated with the naturally occurring photosensitizer riboflavin in all the milk protein preparations studied. The changes in the plasmin-mediated hydrolysis of photooxidized proteins are discussed in relation to changes introduced in the protein structure upon photooxidation. Plasmin-mediated hydrolysis of alpha(S)-casein, consisting of a mixture of alpha(S1)- and alpha(S2)-casein and a preparation of beta-casein, was most highly affected by photooxidation, which is in agreement with the fact that those 2 proteins have been found to be most labile toward photooxidation. Changes in the formation of potential angiotensin-I-converting enzyme-inhibitory peptides as well as peptides proposed to have antibactericidal activities by plasmin were observed by oxidation of milk proteins before plasmin-mediated hydrolysis.
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PMID:Plasmin digestion of photooxidized milk proteins. 1848 39

The objective of the present study was to determine the effect of high pressure (HP) processing (200, 450 and 650 MPa) at various temperatures (20, 40 and 55 degrees C) on the total plasmin plus plasminogen-derived activity (PL), plasminogen activator(s) (PA) and cathepsin D activities and on denaturation of major whey proteins in bovine milk. Data indicated that transfer of both PL and PA from the casein micelles to milk serum occurred at all pressures utilized at room temperature (20 degrees C). In addition to the transfer of PL and PA from micelles, there were reductions in activities of PL (16-18%) and PA (38-62%) for the pressures 450 and 650 MPa, at room temperature. There were synergistic negative effects between pressure and temperature on residual PL activity at 450 and 650 MPa and on residual PA activity only at 450 MPa. Cathepsin D activity in the acid whey from HP-treated milk was in general baroresistant at room temperature. The residual activity of cathepsin D decreased significantly at 650 MPa and 40 degrees C and at the pressures 450 and 650 MPa at 55 degrees C. Synergistic negative effects on the amount of native beta-lactoglobulin were observed at 450 and 650 MPa and on the amount of native alpha-lactalbumin at 650 MPa. There were significant correlations between enzymatic activities (PL, PA and cathepsin D) and the residual native beta-lactoglobulin and alpha-lactalbumin in bovine milk. In conclusion, HP significantly affected the activity of indigenous proteolytic enzymes and whey protein denaturation in bovine milk. Reduction in activity of indigenous enzymes (PL, PA and cathepsin D) and transfer of PL and PA from the casein to milk serum induced by HP is expected to have a profound effect on cheese yield, proteolysis during cheese ripening and quality of UHT milk during storage.
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PMID:Effect of high-pressure treatment at various temperatures on indigenous proteolytic enzymes and whey protein denaturation in bovine milk. 1851 57


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