This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Riedell, W. E. Articles by Miernyk, J. A. Search for Related Content PubMed PubMed Citation Articles by Riedell, W. E. Articles by Miernyk, J. A. Agricola Articles by Riedell, W. E. Articles by Miernyk, J. A.

Metabolism and Enzymology

Glycoprotein Synthesis in Maize Endosperm Cells

The Nucleoside Diphosphate-Sugar: Dolichol-Phosphate Glycosyltransferases

Seed Biosynthesis Research Unit, United States Department of Agriculture, Agricultural Research Service, Northern Regional Research Center, Peoria, Illinois 61604

Microsomal membrane preparations from maize (Zea mays L., inbred A636) endosperm cultures contained enzymes that transferred sugar moieties from uridine diphosphate-N-acetylglucosamine, guanosine diphosphate-mannose, and uridine diphosphate-glucose to dolichol-phosphate. These enzyme activities were characterized with respect to detergent and pH optima, substrate kinetic constants, and product and antibiotic inhibition constants. It was demonstrated by mild acid hydrolysis and high performance liquid chromatography that the products of the N-acetylglucosamine transferases were N-acetylglucosamine-pyrophosphoryl-dolichol and N,N'-diacetyl-chitobiosyl-pyrophosphoryl-dolichol and that the product of the mannose transferase was mannosyl-phosphoryl-dolichol. A large proportion of the products of the glucose transferase activity was stable to mild acid hydrolysis. However, the proportion that was labile was identified as glucosyl-phosphoryl-dolichol. Rate zonal sedimentation and isopycnic banding in linear sucrose density gradients in the presence of 1 millimolar ethylenediaminetetraacetic acid indicated that the glycosyltransferase activities were located in the endoplasmic reticulum. The glycosyltransferases were not solubilized by 500 millimolar KCl or by sequential washes with tris-(hydroxymethyl)aminomethane and water, treatments that release peripheral membrane proteins. Solubilization was achieved with low concentrations of Triton X-100. When sealed microsomal vesicles were incubated with trypsin for 30 minutes in absence of detergent, the activity of N-acetylglucosaminyl-transferase was substantially reduced, while the activity of the glucosyl-transferase was somewhat reduced. Activity of the mannosyl-transferase was resistant to inactivation by incubation with trypsin unless Triton was present.

This article has been cited by other articles:

				R. T. Mullen, C. S. Lisenbee, J. A. Miernyk, and R. N. Trelease Peroxisomal Membrane Ascorbate Peroxidase Is Sorted to a Membranous Network That Resembles a Subdomain of the Endoplasmic Reticulum PLANT CELL, November 1, 1999; 11(11): 2167 - 2186. [Abstract] [Full Text]