Isolation and Partial Characterization of Xanthine Oxidase Associated with the Milk Fat Globule Membrane of Cows’ Milk

Open Access
Publisher Website
Google Scholar
Abstract
Xanthine oxidase was isolated directly from fat globule membranes by freeing the bound enzyme with sodium deoxycholate, obviating the use of proteolytic enzymes in the purification procedure. The isolated enzyme possessed a Km of 1.29 .+-. .08 .times. 10-5 M and a maximum initial velocity of 3.62 .+-. .07 .mu.mol/mg per min. A MW of .apprx. 153,000 was determined by electrophoresis in sodium dodecyl sulfate-containing polyacrylamide gels. Upon storage at 4.degree. C for 30 days or 37.degree. C for 24 h, the molecule degraded into smaller molecular units. The breakdown appears to be independent of microbial load and temperature-dependent association-dissociation phenomena. A membrane-associated protease endogenous to the milk system was implicated as the degrading agent.

This publication has 41 references indexed in Scilit: