Identification of high molecular weight enkephalin percursor forms in human cerebrospinal fluid

An enzyme radioimmunoassay procedure has been used to identify (Leu)- and (Met)enkephalin containing polypeptides in human cerebrospinal fluid (CSF). A large volume of lumbar CSF collected from 15-20 neurologic subjects was fractionated by ion exchange chromatography on Aminex Q-15 and subsequently on Sephadex G-50. The lyophilized fractions were treated with trypsin and the generated enkephalyl hexapeptides were isolated by SP-Sephadex ion-exchange chromatography and quantified by radioimmunoassay specific for (Met)enkephalin-Arg6/Lys6 and (Leu)enkephalin-Arg6, respectively. Confirmation of the structures of the recovered fragments was obtained by HPLC. In total, the procedure yielded about 100 fmole (Met)-enkephalyl and 40 fmole (Leu)enkephalyl hexapeptides per ml CSF. Our results also suggest that the main part of the (Leu)enkephalin related activity emerged from prodynorphin.