ABSTRACT
Two fatty acid binding proteins (FABPs) of identical Mr, 13 kDa, have been isolated from developing human fetal brain. A delipidated 105,000g supernatanwt as incubated with [1 -'4C]oleate and subjectedt o a Sephacryl S-200 column followed by gel filtration chromatography on a Sephadex G-75 column and ion-exchange chromatography using a DEAE-Sephacel column. Purity was checked by UV spectroscopy, SDS-PAGE, isoelectric focusing and immunological cross-reactivity. The two FABPs designated as DE-I (pI 5.4) and DE-n (pI 6.9) showed cross-reactivity with each other and no alteration at the antigenic site during intrauterine development. Anti-human fetal brain FABP does not cross-react with purified human fetal heart, gut, lung or liver FABPs. The molecular mass of DE-I and DE-n is lower than those of fetal lung and liver FABPs. Like liver FABP, these proteins bind organic anions, fatty acids and acyl CoAs but differ in their binding affinities. Both DE-I and DE-n have been found to exhibit higher affinity for oleate (Kd = 0.23 ~M) than palmitate (Kd = 0.9 ~M) or palmitoyl-CoA (Kd = 0.96 ~M), with DE-I binding less fatty acids than DE-n. DE-II is more efficient in transferring fatty acid from phospholipid vesjcles than DE-I indicating that human fetal brain FABPs may playa significant role in fatty acid transport in developing fetal brain.