EMULSIFYING FUNCTION OF LACTOPHORIN AND CONDUCTION OF INHIBITION OF LIPOPROTEIN LIPASE

1992 Fiscal Year Final Research Report Summary

• Project/Area Number: 03660291
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: 畜産化学
• Research Institution: UTSUNOMIYA UNIVERSITY
• Principal Investigator: KANNO Choemon UTSUNOMIYA UNIVERSITY, AGRICULTURE PROFESSOR, 農学部, 教授 (30011969)
• Project Period (FY): 1991 – 1992
• Keywords: BOVINE MILK / LACTOPHORIN / LIPOPROTEIN LIPASE / EMULSIFYING FUNCTION / INHIBITION OF LIPOLYSIS / RANCID FLAVOR / PROTEOSE PEPTONE / MILK FAT GLOBULE MEMBRANE

Research Abstract

Lactophorin (LP) reacts with the antibody of soluble glycoprotein from bovine milk fat globule membrane and present as the major glycoprotein in the component-3 of proteose peptone fraction of milk whey. LP is rich in hydrophobic amino acid residues and possesses saccharide chain which protect coalescence and agglutination of fat globules. In the present study, it has been undertaken to study the emulsifying ability of LP and inhibition of lipoprotein lipase by LP.
1. Emulsifying function Emulsifying ability was evaluated by measuring emulsifying activity, emulsion stability, viscosity, diameter, and specific surface area of globules in emulsion which was prepared by homogenizing a mixture of 1% protein including LP and 25% milk fat in 0.1 M phosphate buffer (pH 7.0) on a Polytron homogenizer (19,500 rpm) at 45ﾟC. 1) LP formed emulsion with higher emulsifying ability at short emulsifying time (30 sec)and 40 mg LP per g of milk fat. 2) Increasing LP concentration, emulsifying properties increased. However, viscosity of emulsion increased. 3) LP formed oil in water emulsion in the range of 10 and 50% milk fat in the level of 40 mg of LP per g fat. 4) Emulsifying ability was influenced by pH; emulsion stability was lowest at pH 4, which in isoelectric point of LP, but high at pH 7-10.5) LP consists of mostly 28 and 18 KDa polypeptides. Major polypeptide adsorbed on the surface of globules in emulsion prepared at pH 7 was 28 KDa and both in emulsion at pH 3, 4, and 9.
2. Inhibition of lipoprotein lipase (LPL) LPL is contained indigenously in fresh bovine milk, but not act on milk fat in the globule which is enveloped with fat globule membrane. However, partially destructed fat globules are easily hydrolyzed by LPL. In this study. indigenous LPL in sonicated milk was utilized for examining the inhibitory action of LP to LPL. 1) Lipolysis in fresh bovine milk was accelerated by sonic treatment. 2) Of proteose-peptone fractions, component-3 fraction enriched in LP showed the inhibitory effect on LPL;LP in 40 mg LP per ml of sonicated milk inhibited about 30% of the release of fatty acid. 3) LP was purified by gel filtration of component-3 fraction. Inhibition to LPL in sonicated milk increased with the increase of purified LP concentration. LP in 40 mg/ml of sonicated milk inhibited about 80% of the release of fatty acid by LPL for 60 min. at 37ﾟC.