The influence of somatic cell count on the heat stability of bovine milk plasmin activity

Kennedy, Anna; Kelly, Alan L.

doi:10.1016/s0958-6946(97)00094-0

Cited by 26 publications

(30 citation statements)

References 10 publications

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“…Specifically, several studies have reported significant protection of plasmin in the presence of sodium caseinate, and enhanced inactivation in the presence of β-lactoglobulin [1,22,29]. Heat inactivation of plasmin in the presence of β-lactoglobulin is thought to be linked to the formation of thiol-disulphide bonds with unfolded β-lactoglobulin [13,16]. Pressurisation also induces unfolding of β-lactoglobulin [9,18], and consequently exposes the highly reactive internal thiol group, which may be able to undergo thiol-disulphide interactions with disulphide groups linking structural subunits in the plasmin molecule.…”

Section: Discussionmentioning

confidence: 99%

“…However, lower pH values, unfolding is less favoured and the protein is protected from extensive interactions [6,9]. On heating milk, it is the sulphydryl group that reacts with plasmin to inactivate the enzyme [16], which suggests that reducing pH should indirectly increase the stability of the enzyme in such systems, if an analogous mechanism to heat inactivation occurs. However, increasing pressure in the presence of β-lactoglobulin decreased residual plasmin activity, which indicates that the inactivation occurred despite the potentially reduced reactivity of denatured β-lactoglobulin with the enzyme at reduced pH.…”

Section: Minsmentioning

confidence: 99%

“…Plasmin is relatively heat stable in simple buffer systems, but is greatly destabilised when heated in the presence of β-lactoglobulin, due to thiol-disulphide interchange reactions between the disulphide bonds within the enzyme structure and the exposed thiol group of denatured β-lactoglobulin [12,16]. This leads to greatly reduced plasmin activity in, for example, ultra-high temperature (UHT) milk [15].…”

Section: Introductionmentioning

confidence: 99%

“…Casein in milk increases the thermal stability of plasmin [1]. The mechanisms and kinetics of thermal inactivation of plasmin have been extensively studied [1,16,22].…”

Section: Introductionmentioning

confidence: 99%

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Barostability of milk plasmin activity

Scollard

Beresford

Murphy

et al. 2000

Lait

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-The influence of high pressure (HP) on the stability and activity of the milk alkaline proteinase plasmin was examined. Assays of enzyme activity following HP treatment of plasmin in phosphate buffer (pH 6.7) indicated that the enzyme was extremely pressure stable, retaining almost all activity even after treatment at 600 MPa for 20 min at 20 °C. Plasmin was also extremely stable when HP treated in buffer containing 25 mg . mL -1 sodium caseinate, and in cheese. However, HP treatment in buffer containing 5 mg . mL -1 β-lactoglobulin resulted in enzyme inactivation at pressures > 400 MPa, indicating that the presence of β-lactoglobulin greatly destabilises the enzyme under high pressure, which is analogous to the effect of this protein on the heat stability of plasmin. In separate experiments, hydrolysis of β-casein by plasmin at 20 °C for 30 min at various pressures (300-800 MPa) was studied. Parallel control incubations were performed at atmospheric pressure. Urea-PAGE analysis of digests showed that primary proteolysis of β-casein was decreased at P > 400 MPa. As judged from RP-HPLC analysis, production of 2%-TCA soluble peptides by plasmin appeared unaffected at P < 700 MPa, above which pressure the rates of peptide production decreased. Overall, plasmin is relatively pressure stable in most systems and can hydrolyse its preferred substrate (β-casein) at pressures up to 700 MPa, but is sensitive to destabilisation by denatured β-lactoglobulin. plasmin / high pressure / specificity / stability Résumé -Stabilité de la plasmine sous l'influence de hautes pressions. L'influence des hautes pressions sur la stabilité et l'activité de la plasmine bovine a été examinée. Les déterminations de l'activité enzymatique suivant le traitement à hautes pressions de la plasmine dans une solution tampon phosphate (pH 6,7) a indiqué que l'enzyme était très résistante à la pression, conservant presque toute son activité, même après un traitement a 600 MPa pendant 20 min à 20 °C. Lorsque la plasmine a été traitée dans une solution tampon contenant 25 mg . mL -1 de caséinate de sodium ou dans le fromage, elle s'est aussi avérée très stable. Cependant, le traitement à hautes pressions dans une Lait 80 (2000) 609-619 609

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Section: Discussionmentioning

confidence: 99%

Section: Minsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Casein in milk increases the thermal stability of plasmin [1]. The mechanisms and kinetics of thermal inactivation of plasmin have been extensively studied [1,16,22].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Barostability of milk plasmin activity

Scollard

Beresford

Murphy

et al. 2000

Lait

Self Cite

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show abstract

“…No entanto, uma taxa acentuadamente maior ocorre em leites com alta CCS (DE RHAM & ANDREWS, 1982). KENNEDY & KELLY (1997) demonstraram que a atividade da plasmina no leite cru com 800.000 células mL -1 foi aproximadamente duas vezes maior que no leite com CCS menor que 150.000 células mL -1 . A plasmina exerce forte ação proteolítica sobre as frações de caseína aS1, aS2 e b, sendo que essa atividade aumenta com a severidade da mastite e, consequentemente, com o aumento da CCS no leite (BASTIAN & BROWN, 1996).…”

Section: Introductionunclassified