In vitro biosynthesis of beta-endorphin, gamma-lipoprotein, and beta-lipotropin by the pars intermedia of beef pituitary glands.

Labeled amino acids were incorporated with proteins during incubations of isolated cells from the pars intermedia of beef pituitary glands. After 3 hr of incubation with methionine and [3H]lysine, approximately equivalent amounts of labeled gamma-lipotropin and beta-endorphins were isolated. They were found to be major synthesis products of the pars intermedia. In contrast, very little labeled beta-lipotropin was recovered. Another major synthesis product of the pars intermedia was also purified. Its partial amino acid sequence and molecular weight were determined and it was concluded that this peptide cannot be identified as any known pituitary hormone or protein fragment.