Date of Award

1973

Document Type

Thesis

Degree Name

Master of Science

Department

Chemistry

Abstract

Ferroxidase-II was definitely identified as a lipoprotein. Cholesterol and phospholipids remained tightly associated with the ferroxidase-II protein following extensive purification. Quantitative analysis showed that it is a high-density lipoprotein. Thin-layer chromatographic analyses indicated that phosphatidylcholine accounts for the majority of the bound phospholipid with lysophosphatidyl choline and sphingomyel in accounting for the remaining phospholipid.

Treatment of purified ferroxidase-II with phospholipase C or A resulted in a loss of ferroxidase activity which paralleled the hydrolysis of phospholipid. Phospholipid D treatment also resulted in the loss of ferroxidase activity, yet the loss was not as great as with other phospholipases. A lipid-depleted form of ferroxidase-II was prepared by acetone extraction, or gel -filtration following treatment with phospholipase C. However, hydrolysis, not removal , of the lipid was sufficient for the loss of ferroxidase activity.

Disc-gel electrophoresis and protein elution patterns from gel ­ filtration columns of the native and lipid-depleted ferroxidase-II demonstrated that no gross structural changes occur during lipid­ depletion. The loss of copper accompanied lipid-depletion. The loss of copper explained the inactivation of ferroxidase-II occurring on hydrolysis and removal of lipids. Reconstitution studies with lipid­ depleted ferroxidase-II indicated that the changes occurring during hydrolvsis and removal of the lipids were not readily reversible.

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