Factors Affecting the Apparent Activity and Heat Sensitivity of Xanthine Oxidase in Milk

Abstract

The apparent activity of xanthine oxidase increased upon storing at 4[degree] C, heating to 70[degree] C for 5 min. and homogenization and incubation with proteolytic and lipolytic commercial enzymes. It was accompanied by activity increases in the skimmilk phase with a corresponding decrease in the fat phase. These changes were apparently due to release of aggregates of enzyme microsomes from the fat globule membrane. The heat sensitivity of xanthine oxidase increased on storage and homogenization. It was believed to involve a disintegration of the enzyme microsomes, whereas increases in activity seems to merely involve a simple dispersal of microsomal aggregates.