PURIFICATION AND CHARACTERIZATION OF A FATTY-ACID BINDING-PROTEIN FROM HUMAN PROSTATIC TISSUE

Epidemiological studies suggest the existence of a strong relationship between the incidence of prostatic cancer and the intake of dietary l ipids in humans. However, very little information is available on intr acellular fatty acid metabolism in human prostatic tissue. The objecti ve 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 tis sue. The purified FABP had an apparent molecular mass of 15.0 +/- 1.0 kDa as averaged from three different methods, sodium dodecylsulfate-po lyacrylamide gel electrophoresis (SDS-PAGE), gel filtration and amino acid analysis. The pI value of the protein was determined to be 6.8. S catchard analysis of fatty acid binding to the purified FABP from mali gnant prostatic tissue showed a Kd value of 0.53 +/- 0.02 muM for arac hidonic acid (n = 5). The Kd values of FABP purified from benign prost atic tissue were 0.57 +/- 0.02 muM for oleic acid and 0.51 +/- 0.04 mu M 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 mal ignant and benign tissues contained the same concentration of FABP. Th e concentrations of FABP in malignant and benign tissues were 19.2 +/- 1.8 and 21.4 +/- 2.1 mug per mg of total cytosolic protein, respectiv ely. Characterization based on amino acid composition, isoelectric poi nt and fluorescence with dansyl undecanoic acid suggests that the FABP may not be of the heart type, but is rather more closely related to t he liver type. As malignant prostatic tissue produces more PGE2 compar ed to benign tissue, our data suggest that FABP may help enhancing the synthesis of the prostaglandin in malignant tissue by facilitating ar achidonic acid transport.