Esterification of D-mannoheptulose confers to the heptose inhibitory action on D-glucose metabolism in parotid cells.

D-mannoheptulose, but not its hexaacetate ester, inhibits, in a competitive manner, D-glucose phosphorylation by either purified beef heart hexokinase or crude parotid gland homogenates. Yet, D-mannoheptulose hexaacetate, but neither the unesterified heptose nor acetate or its methyl ester, inhibits D-[5-3H]glucose utilization and D-[U-14C]glucose conversion to 14CO2 and 14C-labelled acidic metabolites and amino acids in intact isolated parotid cells. It is proposed, therefore, that D-mannoheptulose hexaacetate crosses efficiently the plasma membrane of parotid cells and, after intracellular hydrolysis, allows inhibition of D-glucose phosphorylation by the unesterified heptose. The ester of D-mannoheptulose could thus represent a useful tool to inhibit hexose phosphorylation and interfere with cell growth in cells otherwise resistant to the heptose.