Purification and characterization of a fatty acid binding protein from human prostatic tissue

Abstract

Epidemiological studies suggest the existence of a strong relationship between the incidence of prostatic cancer and the intake of dietary lipids in humans. However, very little information is available on intracellular fatty acid metabolism in human prostatic tissue. The objective of this study was to identify and subsequently characterize a fatty acid binding protein of human prostatic tissue. A fatty acid binding protein (FABP) was purified and characterized from human prostatic tissue. The purified FABP had an apparent molecular mass of 15.0±1.0 kDa as averaged from three different methods, sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), gel filtration and amino acid analysis. The pI value of the protein was determined to be 6.8. Scatchard analysis of fatty acid binding to the purified FABP from malignant prostatic tissue showed a Kd value of 0.53±0.02 μM for arachidonic acid (n=5). The Kd values of FABP purified from benign prostatic tissue were 0.57±0.02 μM for oleic acid and 0.51±0.04 μM for arachidonic acid (n=5). Fatty acid analysis revealed that the level of endogenously bound arachidonic acid was about 2.5-fold higher in FABP from malignant than from benign tissue. In addition, both malignant and benign tissues contained the same concentration of FABP. The concentrations of FABP in malignant and benign tissues were 19.2±1.8 and 21.4±2.1 μg per mg of total cytosolic protein, respectively. Characterization based on amino acid composition, isoelectric point and fluorescence with dansyl undecanoic acid suggests that the FABP may not be of the heart type, but is rather more closely related to the liver type. As malignant prostatic tissue produces more PGE₂ compared to benign tissue, our data suggest that FABP may help enhancing the synthesis of the prostaglandin in malignant tissue by facilitating arachidonic acid transport.