The Incorporation of d-Glucosamine-14C into Root Tissues of Higher Plants

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Abstract
D-Glucosamine-1-14C was rapidly taken up from aqueous solution by both excised bean (Phaseolus vulgaris) and corn (Zea mays) root tips. The labeled glucosamine did not accumulate in the tissues, however, but was metabolized to N-acetyl-d-glucosamine, N-acetyl-d-glucosamine phosphates, and uridine diphosphate N-acetyl-d-glucosamine. Little or no label was detected in respiratory CO2, glycolytic intermediates, or d-glucosamine 6-phosphate. Between 5 and 10% of the 14C was recovered in high molecular weight ethanol-insoluble materials which could be solubilized readily with alkali or by treatment with proteases, and which yielded labeled glucosamine upon complete hydrolysis with HCl. Milder hydrolytic conditions released quantities of N-acetylglucosamine-14C plus labeled fragments of higher molecular weight. It is concluded that d-glucosamine-14C may be used to label specifically the amino sugar residues of plant as well as animal macromolecules. N-Acetyl-d-glucosamine acts similarly as a precursor, except that it is taken up at only about 1/10 the rate of glucosamine and hence is utilized less efficiently.