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The Biosynthesis of Glycoproteins

V. Incorporation of Glucosamine-1-¹⁴C into Macromolecules by Ehrlich Ascites Carcinoma Cells¹

Department of Biological Chemistry, University of Illinois, College of Medicine, Chicago, Illinois

Glucosamine-¹⁴C was rapidly incorporated by Ehrlich ascites carcinoma cells into trichloroacetic acid-insoluble molecules both in vivo and in vitro. Sialic acid and an unidentified compound also became labeled and incorporated into macromolecules, but amino acids were unlabeled.

The incorporation in vitro was promoted by pyruvate and was inhibited by glucose. The inhibition by glucose could be related to a competition between glucose and glucosamine for hexokinase.

The acid-soluble radioactive intermediates derived from glucosamine-¹⁴C in Ehrlich cells were similar to those found in rat liver; UDP-N-acylhexosamines³ were the predominant radioactive components from the earliest time.

Puromycin caused 12–20% inhibition of glucosamine-¹⁴C incorporation into acid-insoluble materials. This inhibition could be increased to about 50% if the cells were preincubated with puromycin.

Among the subcellular fractions, the microsomes were the most highly labeled.

¹ This work was supported by a grant from the NIH (CY2951) and from the Armed Forces Epidemiological Board (MD2133).

³ The abbreviations used are: UDP, uridine diphosphate; EDTA, ethylenediamine tetraacetate; Tris, tris(hydroxymethyl) aminomethane; NANA, N-acetylneuraminic acid; RNA, ribonucleic acid; UMP, uridine monophosphate.

² Career Development Awardee of USPHS.

Received 3/19/65.