Carbohydrate transport in Moniliformis dubius (Acanthocephala). III. Post-absorptive fate of fructose, mannose, and galactose.

The initial metabolism of fructose, mannose, and galactose in Moniliformis dubius (M. moniliformis; Acanthocephala) was examined following brief aerobic incubations in 14C-labeled substrate. The pattern of incorporation of radioactivity from 14C-fructose and 14C-mannose into intermediates of hexose metabolism was indistinguishable from that reported elsewhere for the initial post-absorptive metabolism of 14C-glucose under comparable conditions; these hexoses were phosphorylated rapidly following their absorption, and much of the radioactivity absorbed as mannose or fructose was recovered in the nonreducing disaccharide trehalose [alpha-D-glucopyranosyl-(1 leads to 1)-alpha-D-glucopyranoside]. 14C-Galactose was phosphorylated less readily than the other hexoses. More than half of the radioactivity absorbed as galactose was incorporated into disaccharide; some of the galactose-derived disaccharide had properties suggesting the presence of a galactosyl moiety. Incorporation of radioactivity from any of the hexoses into glycogen was minimal. The extensive incorporation of hexose moieties into trehalose or a trehalose-like disaccharide rather than glycogen underscores the probable importance of trehalose metabolism to carbohydrate assimilation in Moniliformis. Physiological factors which might favor trehalose biosynthesis over glycogenesis are considered.