Hexosamine metabolism during spherule formation in Physarum polycephalum.

Hexosamine metabolism in relation to the spherule-wall synthesis in Physarum polycephalum was studied by the incorporation of labeled sugar into the wall and intermediary compounds in the biosynthesis of wall polysaccharide. The incorporation of [14C]galactosamine into the wall material occurred after a lag period of about 10 h in an induction medium. Nucleotides and sugar phosphates in the acid-soluble fraction of spherulating plasmodia were analyzed by column chromatography on Dowex 1-X8 (formate). The primary labeled products formed in the spherulating plasmodia after incubation with [14C]galactosamine were galactosamine 1-phosphate, UDP-galactosamine, N-acetylhexosamine 6-phosphate and UDP-N-acetylhexosamine. Spherulation was insensitive to polyoxin D, while it was completely blocked by cycloheximide. The activity of galactokinase and galactose-1-phosphate uridyltransferase increased 4--5-fold during the spherulation.