Isolation of an anorexigenic protein from membranes

Although widely distributed in eukaryotic cells glycoproteins appear to be rare in prokaryotic organisms. The prevalence of the misconception that bacteria do not glycosylate their proteins has been a subject matter of discussion for a long time. Glycoconjugates that are linked to proteins or peptides, generated by the ribosomal translational mechanism have been reported only in the last two to three decades in a few prokaryotic organisms. Most studied prokaryotic glycoproteins are the S-layer glycoproteins of Archeabacteria. Apart from these, membrane-associated, surface-associated, secreted glycoproteins and exoenzymes glycoproteins are also well documented in both, Archea and Eubacteria. From the recent literature, it is now clear that prokaryotes are capable of glycosylating proteins. In general, prokaryotes are deprived of the cellular organelles required for glycosylation. In prokaryotes many different glycoprotein structures have been observed that display much more variation than that observed in eukaryotes. Besides following similar mechanisms in the process of glycosylation, prokaryotes have also been shown to use mechanisms that are different from those found in eukaryotes. The knowledge pertaining to the functional aspects of prokaryotic glycoproteins is rather scarce. This review summarizes developments and understanding relating to characteristics, synthesis, and functions of prokaryotic glycoproteins. An extensive summary of glycosylation that has been reported to occur in bacteria has also been tabulated. Various possible applications of these diverse biomolecules in biotechnology, vaccine development, pharmaceutics and diagnostics are also touched upon.

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Bacterial glycoproteins: Functions, biosynthesis and applications

Upreti¹,

Kumar²,

Shankar³

2003

Proteomics

152

115

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A novel plant membrane proteoglycan which causes anorexia in animals

Kidwai

Upreti

1993

Mol Cell Biochem

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Hunger and satiety are complex interplay of several factors in human and animal species. Reduced food intake has also been observed under various pathological conditions. Earlier, we have been able to isolate an endogenous glycoprotein from erythrocyte membranes, which causes anorexia in rats. In the present study, a similar anorexigenic proteoglycan from Mung bean sprout membranes has been isolated and purified. The proteoglycan (50 kDa) consisted of 70-85% carbohydrate with galactose, glucose galactosamine and mannose as the main sugars. Protein part on analysis showed higher glutamic acid and serine content. This proteoglycan reduces food intake when injected in rats deprived of food for 96 hr as well as normally fed rats, mice and rabbits without any rebound. The TCA-soluble proteoglycan from different plant sources have also been compared for their anorexigenic activity. The similarities observed among plant and animal cell membrane proteoglycans with satietins isolated from human blood plasma could be due to membrane origin of satietins.

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A step towards developing the expertise to control hunger and satiety: Regulatory role of satiomem?A membrane proteoglycan

Upreti

Kidwai

1995

Neurochem Res

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Regulation of hunger and satiety is a complex process thought to be controlled by a complex interplay of neurotransmitters in the hypothalamic region of the brain. Reduced food intake or anorexia has also been observed under various disease or disorder conditions including AIDS and cancer. On the other hand, increased appetite because of some impairment of central mechanisms regulating the food intake could also cause/obesity. A large number of substances including neuropeptides, hormones, drugs, and synthetic peptides have been implicated in the regulation of appetite and food intake behavior in normal as well as disease or disorder conditions. Most of these substances are not directly involved in the regulation of normal hunger and satiety but exert their effect indirectly via other media. Some of them are involved under certain pathologic conditions and during the course they become involved directly or indirectly in the triggering of hunger and satiety regulatory mechanism. Recently, we have been able to isolate and purify an endogenous proteoglycan from membranes of animal and plant sources. This membrane anchored proteoglycan termed as 'Satiomem' reduces food intake without any rebound effects and has no apparent toxicity. It also fulfils all the criteria of a true satiety or anorexigenic substance. The release of satiomem from the cell surface could be mediated by a specific phospholipase-C. Satiomem seems to be involved in transducing activating signals and may also act as a source of second messenger for the regulatory mechanism of appetite. This article summarizes the regulatory aspects of hunger and satiety mechanisms controlled by endogenous substances with the emphasis on our present knowledge about satiomem.

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Isolation of an anorexigenic protein from membranes

Cited by 5 publications

References 16 publications

Bacterial glycoproteins: Functions, biosynthesis and applications

Bacterial glycoproteins: Functions, biosynthesis and applications

A novel plant membrane proteoglycan which causes anorexia in animals

A step towards developing the expertise to control hunger and satiety: Regulatory role of satiomem?A membrane proteoglycan

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