Cell-surface glycosyltransferases in gastrulating chick embryos: II. Biochemical evidence for a surface localization of endogenous glycosyltransferase activities☆☆☆

[摘要] Intheprecedingpaper[Shur,B.D.(1977).Cellsurfaceglycosyltransferasesingastrulatingchickembryos.I.Temporallyandspatiallyspecificpatternsoffourglycosyltransferaseactivities.Develop.Biol.58,23–39].sevendifferentclassesofglycosyltransferaseswereassayedautoradiographicallyingastrulatingchickembryos.Fourtransferasesproducedtemporallyandspatiallyspecificpatternsofendogenousactivitywhichweremostintenseonactivelymigratingcelltypes.Thedatapresentedinthismanuscriptindicatethattheavailablelevelsofsugar-phosphateandfreesugarresultingfromsugarnucleotidehydrolysiswereinsufficienttoaccountfortheobservedpatterns.Resultswith(i)competitivepyrophosphataseinhibitors,(ii)reconstructionexperimentscontainingthepotentialcontributionoflabeledfreesugarandsugar-phosphate,(iii)hexosetransportinhibitors,and(iv)excessesofunlabeledsugarsandsugar-phosphatesallsuggest,alongwithadditionalcontrols,thatsugarnucleotidebreakdownproductswerenotmajorcontributorstothetotalsugarsincorporatedduringsugarnucleotideincubations.Theenzyme:substratecomplexesassayedduringthesesugarnucleotideincubationsarelikelytobeextracellularsince(A)noevidenceexistsforintactsugarnucleotidetransportintothesecells,and(B)neithersupernatantnorhomogenateglycosyltransferaseactivitiescouldaccountfortheautoradiographs.

[学科分类] 生物科学（综合）