Basic description
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Apolipoprotein D (APO D), a glycoprotein involved in the human plasma lipid transport system. It is a progesterone binding glycoprotein of 24,000 dalton monomer molecular size, is a constituent of density lipoprotein in plasma. The function of apolipoprotein D in the metabolism of plasma lipoproteins is unclear but the observation that this protein forms complexes with lecithin: cholesterol acyltransferase has led to the suggestion that apolipoprotein D may be involved in cholesterol esterification and transport of substrates and products of the reaction. Apolipoprotein D is expressed in a range of normal tissues including axillary apocrine glands, adrenal cortex and corpus luteum. Peripheral nerves, pituitary, testis, cerebellum and renal tubes are also positive. APO D was first isolated in large quantity as GCDFP 24, the major protein component of more human breast cyst fluids. In recent studies, Apo D immunoreactivity has been shown to be an early indicator of prostate cancer and advanced primary prostate tumors.
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