Glycoprotein synthesis in plants. I. Role of lipid intermediates
The enzymic processes involved in glycoprotein synthesis have been studied using crude extracts obtained from developing cotyledons of Phaseolus vulgaris harvested at the time of active deposition of vicilin. Radioactivity from GDP-(/sup 14/C)mannose can be incorporated by crude extracts into a single chloroform-methanol-soluble product as well as into insoluble product(s). Mannose is the sole /sup 14/C-labeled constituent of the lipid. The kinetics of incorporation of /sup 14/C, as determined by pulse and pulse-chase experiments using GDP-(/sup 14/C)mannose, as well as direct incorporation from added (/sup 14/C)mannolipid, shows that the mannolipid is an intermediate in the synthesis of the insoluble product(s). The characteristics of the mannolipid are consistent with it being a mannosyl phosphoryl polyprenol. The mannose is apparently attached to the lipid via a monophosphate linkage. Of the radioactivity in the insoluble product(s), about 20 percent is pronase-digestible during a ''pulse experiment.'' After a chase with unlabeled GDP-mannose, about 40 percent is pronase-digestible; the other 60 percent is as yet uncharacterized. A radioactive product soluble in a mixture of chloroform-methanol-H/sub 2/O can be extracted from the insoluble residue obtained during a pulse, but is no longer present after a chase. This product may be a lipid oligosaccharide, the final intermediate in glycoprotein synthesis. Data are presented on incorporation from UDP-N-(/sup 14/C)acetylglucosamine into both chloroform-methanol-soluble and -insoluble product(s). The results are consistent with an involvement of lipid intermediates in the glycosylation of protein in this system, and support the concept that the mechanisms of glycoprotein synthesis in higher plants are similar to those which have been reported for mammalian systems.
- Research Organization:
- Michigan State Univ., East Lansing, MI (United States)
- OSTI ID:
- 7306930
- Journal Information:
- Plant Physiol.; (United States), Vol. 59:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GLUCOPROTEINS
BIOSYNTHESIS
PLANTS
BIOCHEMICAL REACTION KINETICS
CARBON 14
CATALYSIS
ENZYMES
LABELLING
LIPIDS
MAMMALS
MANNOSE
METABOLISM
ALDEHYDES
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOMASS
CARBOHYDRATES
CARBON ISOTOPES
ENERGY SOURCES
EVEN-EVEN NUCLEI
HEXOSES
ISOTOPES
KINETICS
LIGHT NUCLEI
MONOSACCHARIDES
NUCLEI
ORGANIC COMPOUNDS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RENEWABLE ENERGY SOURCES
SACCHARIDES
SYNTHESIS
VERTEBRATES
YEARS LIVING RADIOISOTOPES
550200* - Biochemistry