Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.52 (PNGase F)
 1,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Four isoforms of glycosylated prolactin (G-pPRL) were isolated from porcine pituitary glands by affinity chromatography and concanavalin A-Sepharose, based upon differences in their affinity for the lectin. Structural analysis indicated differences in the carbohydrate units of the four G-pPRLs. N-glycanase treatment cleaved the oligosaccharide from the G-pPRLs, establishing N-linked glycosylation. The binding of G-pPRLs to receptors from lactating rabbit mammary glands was only 3-8% that of nonglycosylated pPRL (NG-pPRL). The immunological crossreactivity of the G-pPRLs varied from 36 to 65% that of NG-pPRL. When tested in the pigeon crop sac bioassay, G-pPRLs were only 11-40% as active as NG-pPRL. The metabolic clearance rate of one of the G-pPRLs was slower and another faster than that of NG-pPRL. We conclude that there are several forms of G-PRL of variable immuno- and bio-potencies in the porcine pituitary, and that the current radioimmunoassay for the hormone does not measure the actual bioactivity.
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PMID:Isolation and biochemical properties of four forms of glycosylated porcine prolactin. 195 78

The extraembryonic coelomic fluid (EECF) represents a major compartment in the fetal-placental unit during the first trimester of pregnancy. The compartment is composed of the fluid contained between the chorionic and amniotic membranes. The levels of glycoprotein hormone free alpha-subunit and free beta-subunit in the EECF far exceed those in the amniotic fluid or maternal serum. Furthermore, the level of free alpha in this compartment is twice that of intact hCG. We purified the glycoprotein hormone free alpha-subunit from a pool of EECF. This free alpha-subunit was found to be larger in size than the alpha-subunit of intact hCG. The size difference was observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reduced and denatured conditions. The carbohydrate composition of the EECF free alpha-subunit indicated a higher degree of oligosaccharide branching, as evidenced by larger amounts of fucose, sialic acid, galactose, and N-acetylglucosamine than were present on combined hCG alpha. These differences in size and carbohydrate composition argue strongly against the concept that free alpha-subunits might originate from dissociation of intact hCG or "nicked" hCG. The free subunits of the EECF were evaluated for their ability to combine with the corresponding subunit obtained by dissociation of intact hCG. EECF free beta was able to combine with hCG alpha to form intact hCG. In contrast, EECF free alpha was unable to combine with hCG beta to form intact hCG. However, after removal of the asparagine-linked glycans by treatment with N-glycanase, most of the previously uncombinable free alpha-subunits were able to combine with hCG beta. These data demonstrate that the N-linked oligosaccharide(s) of EECF free alpha function to prevent the molecule from combining with the available and combinable free beta-sub-units that coexist in the same physiological compartment during early pregnancy. In view of the large amount of free alpha that is present in the EECF and the observation that, in vitro, free alpha can stimulate uterine decidual cell PRL secretion, together with the close apposition of free alpha-producing cells to decidual cells, it is likely that EECF free alpha has a function in early pregnancy. Carbohydrate modifications generated during the biosynthesis of EECF free alpha-subunit ensure that a population of free alpha molecules can exist in the presence of substantial quantities of free beta-subunits, and correspondingly, these same carbohydrate modifications function to permit the existence of free beta-subunits in the same gestational compartment with free alpha molecules.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The role of glycosylation in regulating the glycoprotein hormone free alpha-subunit and free beta-subunit combination in the extraembryonic coelomic fluid of early pregnancy. 753 82