The Fat-Globule Membrane of Milk: Alkaline Phosphatase and Xanthine Oxidase in Skimmilk and Cream

Zittle, Charles A.; Dellamonica, E. S.; Custer, J.H.; Rudd, Roya

doi:10.3168/jds.s0022-0302(56)94781-6

Cited by 35 publications

(10 citation statements)

References 18 publications

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“…The association of xanthine oxidase with the milk-fat-globule membrane is well established (Ball, 1939;Morton, 1954;Zittle et al, 1956;Dowben et al, 1967). The present results show that approximately half of the xanthine oxidase present in buttermilk is associated with the particulate fraction BM1.…”

Section: Discussionsupporting

confidence: 67%

“…Its composition and mechanism of action are now relatively well understood (Bray, 1963;Massey et al, 1969). In milk much of this enzyme is known to be associated with the fat-globule membrane (Morton, 1954;Zittle et al, 1956). This membrane is considered to be directly derived from the plasma membrane (Keenan et al, 1971) which envelops the fat-globule as it is released from the secretory cell of the mammary gland.…”

Section: Association Of Xanthine Oxidase With the Bovinementioning

confidence: 99%

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Association of xanthine oxidase with the bovine milk-fat-globule membrane. Catalytic properties of the free and membrane-bound enzyme

Briley

Eisenthal

1974

Biochemical Journal

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1. The catalytic properties of xanthine oxidase in bovine milk (EC 1.2.3.2) are dependent on the state of the enzyme, i.e. whether free or bound to the fat-globule membrane. Oxidase activity of the membrane-bound enzyme towards NADH is enhanced relative to that towards xanthine. This reflects a change in the relative K(m) values and enables the ratio of xanthine to NADH oxidase activities (X/N) to be used as a parameter for the relative amounts of free and membrane-bound xanthine oxidase in milk fractions. 2. Chromatography of buttermilk on Sepharose 2B yielded an excluded fraction, BM(1), with xanthine oxidase activity. The remaining xanthine oxidase activity was eluted as a single broad peak. This was further resolved on Sephadex G-200 into an excluded fraction, BM(2), and free xanthine oxidase. Fractions BM(1) and BM(2) had X/N values in the range 45-65, which is characteristic of membrane-bound xanthine oxidase. Purified xanthine oxidase has a mean X/N value of 110.3. Addition of fraction BM(1), heated to remove associated enzyme activities, to purified xanthine oxidase progressively enhanced its NADH oxidase activity to a value where its X/N value was characteristic of membrane-bound xanthine oxidase. This was shown to be due to binding of free enzyme to heated fraction BM(1). The binding constant and stoicheiometry were determined. 4. Proteolytic digestion of fraction BM(1) liberated free xanthine oxidase from the fat-globule membrane with a corresponding alteration in X/N value.

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Section: Discussionsupporting

confidence: 67%

Section: Association Of Xanthine Oxidase With the Bovinementioning

confidence: 99%

Association of xanthine oxidase with the bovine milk-fat-globule membrane. Catalytic properties of the free and membrane-bound enzyme

Briley

Eisenthal

1974

Biochemical Journal

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“…Kay and Graham (1933) observed that AlP is concentrated in cream and released into buttermilk on churning (in fact about 50% of AlP is in the skimmed milk but the specific activity is higher in cream). Zittle and DellaMonica (1952) partially purified AlP from whey and Morton (1950) showed that lipoprotein particles, which he called ''microsomes'' (Morton, 1953), are a rich source of AlP, and many other indigenous enzymes (Morton, 1953;Zittle, DellaMonica, Custer, & Rudd, 1956). The ''microsomes'' are, in fact, portions of the outer layer of the MFGM that have been shed into the serum phase, from which they can be recovered by ultracentrifugation.…”

Section: Milk Alkaline Phosphatasementioning

confidence: 97%

Indigenous enzymes in milk: Overview and historical aspects—Part 2

Fox

Kelly

2006

International Dairy Journal

101

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Between 1924 and about 1970, many indigenous enzymes were identified in milk. These were important as indicators of the adequate pasteurisation of milk (alkaline phosphatase, g-glutamyl transferase) or of mastitis (N-acetylglucosaminidase, acid phosphatase) and some were considered to be important for the stability of milk (superoxidase dismutase, sulphydryl oxidase). Human and equine milk both contain a very high level of lysozyme, which is considered to have a significant protective effect on the neonate. 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 in this article. r

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“…1, and about ten times the nucleic acid content of microsomes from mixed herd milk (see Tables 2 and 4). Zittle, Della Monica, Custer & Rudd (1956) also found that the nucleic acid of microsomes from cornmercial mixed milk was very low. In earlier studies, Morton (1954) had found that microsomes from Jersey milk had quite a high nucleic acid content.…”

Section: Relationship Between Microsome8 Of Milk and Mammary Glandmentioning

confidence: 96%

Comparative properties of microsomes from cow's milk and from mammary gland. 2. Chemical composition

Bailie

Morton

1958

Biochemical Journal

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The Fat-Globule Membrane of Milk: Alkaline Phosphatase and Xanthine Oxidase in Skimmilk and Cream

Cited by 35 publications

References 18 publications

Association of xanthine oxidase with the bovine milk-fat-globule membrane. Catalytic properties of the free and membrane-bound enzyme

Association of xanthine oxidase with the bovine milk-fat-globule membrane. Catalytic properties of the free and membrane-bound enzyme

Indigenous enzymes in milk: Overview and historical aspects—Part 2

Comparative properties of microsomes from cow's milk and from mammary gland. 2. Chemical composition

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