Promotion of conidia aggregation in Aspergillus niger by cyclic AMP and 5'-GMP

Cholesterol and phospholipids remain tightly associated with the ferroxidase-II protein from human serum following extensive purification. Purified ferroxidase-II preparations show a consistent ratio of protein, phospholipid, and cholesterol. Thin-layer chromatographic analyses indicate that phosphatidyl choline accounts for 70% of the bound phospholipid. Treatment of purified ferroxidase-II with phospholipase C or A results in a loss of ferroxidase activity which parallels the hydrolysis of phospholipid. A lipid-depleted form of ferroxidase-II can be prepared by gel-filtration following treatment with phospholipase C. However, hydrolysis, not removal, of the lipid is sufficient for the loss of ferroxidase activity. These studies indicate that the bound lipid components are essential to the maintainence of the catalytic activity of ferroxidase-II.