Detection of two endorphin-like peptides in nucleus caudatus

Two endorphin-like peptides with molecular weight larger than [met5]-enkephaiin were detected in bovine caudate. They were separated from [met5]-enkephal in by Biogel P-2 column chromatography and detected with a [met5]-enkephaiin antibody which possesses some affinity for endorphins larger than [met5]-enkephaiin but smaller than β-endorphin. Our antibody has some affinity for α-endorphin but we can exclude that the two new peptides are α, β-endorphin or β-lipotropin. It is suggested that in nucleus caudatus the two endorphin-like peptides we have detected may function as precursors of [met5]-enkephalin.