Indigenous Proteinases in Milk
01 Jan 2003-pp 495-521
TL;DR: This chapter will review recent research on plasmin and its role in the quality of dairy products and will focus also on other indigenous proteinases, which have not been reviewed thoroughly elsewhere.
Abstract: The presence of indigenous proteolytic activity in milk has been recognized since the work of Babcock and Russel in 1897. Some early researchers attributed this activity to bacterial enzymes, but later work proved conclusively the presence of indigenous proteinases in milk. More recent research has indicated two major categories of indigenous proteolytic enzymes in milk, both originating from the animal’s blood. The major enzyme system contains plasmin, which is produced by activation of its inactive precursor, plasminogen, an event which is under the control of a complex system of inhibitors and activators. The presence of plasmin in milk and its significance to the quality of dairy products has been recognized for many decades (see Bastain and Brown, 1996, for review) and has thus been the subject of much research. However, the other indigenous proteolytic enzymes in milk, which originate from somatic cells, have been studied in detail only during the last decade. Somatic cells, the principal physiological function of which is the defence of the udder against bacterial infection, have lysosomes which contain active proteolytic enzymes, including elastase, collagenase and cathepsins B, D, G, H and L. The acid proteinase originating from somatic cells, cathepsin D, has been studied most thoroughly in milk. However, it is highly likely that the other proteinases known to be present in lysosomes are also present in milk, as has been demonstrated by the recent identification of immunoreactive cathepsin B in milk (Magboul et al., 2001) and observations of the activity of other indigenous thiol proteinases in milk. This chapter will review recent research on plasmin and its role in the quality of dairy products and will focus also on other indigenous proteinases, which have not been reviewed thoroughly elsewhere.
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TL;DR: A review of the biochemical changes that occur in rennet-coagulated cheeses during ripening can be found in this article, with a focus on secondary reactions such as the production of volatile flavour compounds.
Abstract: Rennet-coagulated cheeses are ripened for periods ranging from about two weeks to two or more years depending on variety. During ripening, microbiological and biochemical changes occur that result in the development of the flavour and texture characteristic of the variety. Biochemical changes in cheese during ripening may be grouped into primary (lipolysis, proteolysis and metabolism of residual lactose and of lactate and citrate) or secondary (metabolism of fatty acids and of amino acids) events. Residual lactose is metabolized rapidly to lactate during the early stages of ripening. Lactate is an important precursor for a series of reactions including racemization, oxidation or microbial metabolism. Citrate metabolism is of great importance in certain varieties. Lipolysis in cheese is catalysed by lipases from various source, particularly the milk and cheese microflora, and, in varieties where this coagulant is used, by enzymes from rennet paste. Proteolysis is the most complex biochemical event that occurs during ripening and is catalysed by enzymes from residual coagulant, the milk (particularly plasmin) and proteinases and peptidases from lactic acid bacteria and, in certain varieties, other microorganisms that are encouraged to grow in or on the cheese. Secondary reactions lead to the production of volatile flavour compounds and pathways for the production of flavour compounds from fatty acids and amino acids are also reviewed.
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Cites background from "Indigenous Proteinases in Milk"
...The indigenous aspartyl proteinase, cathepsin D, has received considerable attention in recent years (see reviews by Hurley et al. 2000a; Kelly and McSweeney 2003)....
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...Somatic cells contain many proteinases including cathepsins B, D, G, H, L and elastase (Kelly and McSweeney 2003)....
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...Cathepsin D is a typical mammalian proteinase and is produced autocatalytically from a precursor, procathepsin D, to pseudocathepsin D and thence by thiol proteinases to a number of mature forms (Kelly and McSweeney 2003)....
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TL;DR: Progress on the isolation and characterisation of these seven enzymes first isolated in the period 1925-1970, as well as ribonuclease, aldolase and glutathione peroxidase, from the milk of the cow and other species and their significance in milk and dairy products is reviewed.
251 citations
TL;DR: The results of this experiment demonstrate that the PL activity in ewes milk is markedly influenced by the SCC, although SCC is not the only parameter for predicting PL and PG evolution in ewe milk.
119 citations
TL;DR: Data accumulated during the last 5 years shows that milk indigenous enzymes play a key role in regulating lactogenesis, e.g., inducing active involution, and that they are essential components of antioxidation and the innate immune system of milk.
117 citations
Cites background from "Indigenous Proteinases in Milk"
...The close proximity of plasmin to its substrate ensures that hydrolysis is an efficient process (Korycka-Dahl, Dumas, Chene, & Martal, 1983) and it is the primary agent of proteolysis in goodquality milk (Kelly & McSweeney, 2003)....
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TL;DR: The immune function of somatic cells in the udder defense and their protective role in milk will be primarily considered and different characteristics of milk induced by various somatic cell counts, types, and their endogenous enzymes influencing directly the technological properties of milk and the final quality of dairy products will be discussed.
Abstract: Somatic cells are an important component naturally present in milk, and somatic cell count is used as an indicator of udder health and milk quality. The role of somatic cells in dairy processes and products is ill-defined in most studies because the role of these cells combines also the concomitance of physicochemical modifications of milk, bacterial count, and the udder inflammation in the presence of high somatic cell count. The aim of this review is to focus on the role of somatic cells themselves and of endogenous enzymes from somatic cells in milk, in dairy transformation processes, and in characteristics of final products overcoming biases due to other factors. The immune function of somatic cells in the udder defense and their protective role in milk will be primarily considered. Different characteristics of milk induced by various somatic cell counts, types, and their endogenous enzymes influencing directly the technological properties of milk and the final quality of dairy products will be discussed as well. By comparing methods used in other studies and eliminating biases due to other factors not considered in these studies, a new approach has been suggested to evaluate the effective role of somatic cells on dairy processes and products. In addition, this new approach allows the characterization of somatic cells and their endogenous enzymes and, in future research, will allow the clarification of mechanisms involved in the release of these components from somatic cells during dairy processes, particularly in cheese technologies.
111 citations
References
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TL;DR: Two types of purification methods for Cathepsin B, CathePSin H, and Cathepsypsin L are described: method I is applicable to large amounts of frozen tissues, whereas method II is used with flesh tissue and takes advantage of a 50-fold purification factor attainable by isolation of lysosomes.
Abstract: Publisher Summary This chapter describes two types of purification methods for Cathepsin B, Cathepsin H, and Cathepsin L. Method I is applicable to large amounts of frozen tissues, whereas method II is used with flesh tissue and takes advantage of a 50-fold purification factor attainable by isolation of lysosomes: it has the further advantage of separating the enzymes from inhibitors that are present in the cytosol and plasma. In first purification method, cathepsins B and H are purified from human liver. Method II involves purification of Cathepsins B, H, and L from rat liver. Method I include: extraction, autolysis, and acetone fractionation and DEAE-cellulose chromatography. The pool of cathepsin B from DEAE-cellulose is further purified by covalent chromatography on a column of aminophenylmercuric acetate coupled to Sepharose. Method II include: homogenization and cell fractionation gel; chromatography on Sephadex G-75; CM-Sephadex chromatography; chromatography of cathepsin L on concanavalin A-Sepharose. Cathepsin B can be with BZ-DL-Arg-NPhNO2 or Bz-Arg-2-NNap as substrate, wheras, Cathepsin H can be assayed selectively by use of an unblocked substrate such as Leu-NNap, Arg-NNap, or Arg-NMec. Three synthetic substrates have been used for cathepsin L assay: Bz-Arg-NH2, Z-Lys-OPhNO2, and Z-Phe-Arg-NMec.
1,554 citations
TL;DR: Because of increased interest in milk proteins of species other than bovine, the Committee suggests that these be identified as homologs of those already characterized in European, Bos taurus , and Indian, Bos indicus , cattle.
870 citations
TL;DR: It is suggested, that vital functions of cathepsin D are exerted by limited proteolysis of proteins regulating cell growth and/or tissue homeostasis, while its contribution to bulk proteolytic in lysosomes appears to be non‐critical.
Abstract: Mice deficient for the major lysosomal aspartic proteinase cathepsin D, generated by gene targeting, develop normally during the first 2 weeks, stop thriving in the third week and die in a state of anorexia at day 26 +/- 1. An atrophy of the ileal mucosa first observed in the third week progresses towards widespread intestinal necroses accompanied by thromboemboli. Thymus and spleen undergo massive destruction with fulminant loss of T and B cells. Lysosomal bulk proteolysis is maintained. These results suggest, that vital functions of cathepsin D are exerted by limited proteolysis of proteins regulating cell growth and/or tissue homeostasis, while its contribution to bulk proteolysis in lysosomes appears to be non-critical.
432 citations
TL;DR: In this article, Proteolysis in cheese during ripening is investigated. But it is not shown to be present in the case of sourdough, and the results are limited.
Abstract: (1996). Proteolysis in cheese during ripening. Food Reviews International: Vol. 12, No. 4, pp. 457-509.
427 citations
TL;DR: Plasmin is secreted as plasminogen that is activated in blood and milk and its role in blood is to proteolytically break down blood clots.
311 citations