Temporal Pattern of Incorporation of 3H Precursors into Pituitary Glycoproteins and Their Subsequent Release

Abstract

The temporal pattern of incorporation of various 3H precursors into glycoproteins by rat anterior pituitaries incubated in vitro and the release of 3H-glycoproteins was examined. [3H]Leucine incorporation was linear with respect to time and [3H]leucinecontaining macromolecules appeared in the media in about 1 hr. The temporal pattern of [3H]mannose incorporation and release was similar to that observed for [3H]leucine consistent with [3H]mannose incorporation via the chitobiose core. [3H]Galactose and [3H]fucose were incorporated after apparent time delays of approximately 15 min and soon thereafter (20-25 min) appeared in the medium in 3H-glycoproteins. Thus, these precursors appear to be added as terminal residues. [3H]Glucosamine exhibited a pattern intermediate between [3H]leucine and [3H]fucose whereas [3H]GlcNAc appeared to be incorporated as a terminal residue. 452