TY - JOUR
T1 - κ-Casein interactions in the suspension of the two major calcium-sensitive human β-caseins
AU - Sood, S. M.
AU - Erickson, G.
AU - Slattery, C. W.
N1 - Autorías: G. Erickson, S. M. Sood, C. W. Slattery. Localización: Journal of dairy science. Nº 7, 2003. Artículo de Revista en Dialnet.
PY - 2003/7
Y1 - 2003/7
N2 - The possible effects of both the β-casein (β-CN) phosphorylation level and the κ-CN glycosylation level on micelle formation were studied using the doubly-phosphorylated form (β-CN-2P) and the quadruply- phosphorylated form (β-CN-4P) of human β-CN, along with bovine κ-CN to compare with previous studies using the more highly glycosylated human κ-CN. Addition of bovine κ-CN to human β-CN-2P, β-CN-4P, or a 1/1 (wt/ wt) mixture of the two was at κ/β molar ratios from 0.0 to ∼0.6 and micelles were reconstituted by addition of Ca+2 either directly at 37°C for determination of the fraction suspended or at an initial temperature of 4° that was gradually increased to 37°C with the change in particle size monitored by turbidity measurements. Analysis of the data indicates that the 4P form requires more κ-CN for stabilization than the 2P form but that the mixture of the two is more like the 4P form in that lateral κ-κ interactions may enhance β-κ interactions and micelle formation. Above a κ/β molar ratio of about 0.2, the caseins were fully suspended into reconstituted micelles. However, micelle size decreased at a higher ratio, indicating that the κ-CN probably occupies a surface position and may regulate micelle size by its relative abundance. A comparison with published results suggests that the higher glycosylation level of human κ-CN may protect a larger surface area and result in smaller micelles. Changes in reconstituted micelle size with pH indicate that positively charged groups in the κ-CN may interact with the negatively charged phosphate esters in the β-CN moieties in addition to κ-β hydrophobic interactions.
AB - The possible effects of both the β-casein (β-CN) phosphorylation level and the κ-CN glycosylation level on micelle formation were studied using the doubly-phosphorylated form (β-CN-2P) and the quadruply- phosphorylated form (β-CN-4P) of human β-CN, along with bovine κ-CN to compare with previous studies using the more highly glycosylated human κ-CN. Addition of bovine κ-CN to human β-CN-2P, β-CN-4P, or a 1/1 (wt/ wt) mixture of the two was at κ/β molar ratios from 0.0 to ∼0.6 and micelles were reconstituted by addition of Ca+2 either directly at 37°C for determination of the fraction suspended or at an initial temperature of 4° that was gradually increased to 37°C with the change in particle size monitored by turbidity measurements. Analysis of the data indicates that the 4P form requires more κ-CN for stabilization than the 2P form but that the mixture of the two is more like the 4P form in that lateral κ-κ interactions may enhance β-κ interactions and micelle formation. Above a κ/β molar ratio of about 0.2, the caseins were fully suspended into reconstituted micelles. However, micelle size decreased at a higher ratio, indicating that the κ-CN probably occupies a surface position and may regulate micelle size by its relative abundance. A comparison with published results suggests that the higher glycosylation level of human κ-CN may protect a larger surface area and result in smaller micelles. Changes in reconstituted micelle size with pH indicate that positively charged groups in the κ-CN may interact with the negatively charged phosphate esters in the β-CN moieties in addition to κ-β hydrophobic interactions.
KW - Bovine κ-casein
KW - Human β-casein
KW - Protein-ion interactions
KW - Protein-protein interactions
KW - Reconstituted milk micelles
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U2 - 10.3168/jds.S0022-0302(03)73818-1
DO - 10.3168/jds.S0022-0302(03)73818-1
M3 - Article
C2 - 12906042
SN - 0022-0302
VL - 86
SP - 2269
EP - 2275
JO - Journal of Dairy Science
JF - Journal of Dairy Science
IS - 7
ER -