Purification of a human urinary glycoprotein with gastric antisecretory activity

The human urinary epidermal growth factor (EGF) precursor. Isolation of a biologically active 160-kilodalton heparin-binding pro-EGF with a truncated carboxyl terminus

In this report, we describe the isolation from human urine of a predominant 160-kDa epidermal growth factor (EGF)-immunoreactive glycoprotein that exhibits affinity for heparin. The purification procedure involved concentration and dialysis of 20-30-liter batches of fresh urine on a high capacity ultrafiltration apparatus followed by chromatography on DEAE-Sephacel, heparin-agarose, and Sephacryl S-300. A nearly homogeneous preparation of 160-kDa protein was obtained with a yield of approximately 1 mg of 160-kDa protein from 25 liters of urine. The amino-terminal sequence of the purified 160-kDa protein, H2N-SAPQHXSXPEGTXA-, matched residues 21-34 of the predicted sequence of human prepro-EGF and established that the 160 kDa protein (pro-EGF) is a product of the prepro-EGF gene. Characterization of the carboxyl terminus of the purified protein by digestion with carboxypeptidase B and by immunoblotting with antisera against synthetic carboxyl-terminal and juxtatransmembrane peptides of prepro-EGF indicated that the carboxyl terminus has been truncated at an arginine residue that corresponds, most likely, to the carboxyl-terminal arginine of the EGF moiety. The intact 160-kDa pro-EGF is biologically active as evidenced by its specific binding to the EGF receptor and activation of the EGF receptor tyrosine kinase in A-431 cell membranes. Purified pro-EGF competitively inhibited the binding of 125I-EGF to human fibroblasts, and it stimulated the proliferation of these cells in culture. When immobilized onto culture dishes, the heparin-binding pro-EGF appeared to function both as an adhesion molecule and as a growth factor for serum-free mouse embryo cells.

Purification and characterization of epidermal growth factor (beta-urogastrone) and epidermal growth factor fragments from large volumes of human urine

We purified human epidermal growth factor (hEGF) and hEGF fragments from a benzoic acid precipitate of the materials not adsorbed to silica gel in 330 liters of human urine by a relatively brief, simple, and efficient method employing sequential batch absorption to and stepwise elution from CM-cellulose and DEAE-cellulose, Bio-Gel P-10 chromatography in 50 mM HCl, and three reverse-phase HPLC steps for final resolution and purification of hEGF components. Recovery of hEGF was 29%. Eight apparently homogeneous hEGF components were recovered, each of which had similar activities in a homologous hEGF radioimmunoassay and an EGF radioreceptor assay using human placental membranes. Amino acid composition analysis indicated that there were four pairs of components that represented intact 53-amino acid hEGF, hEGF-(1-52), hEGF-(1-51), and hEGF-(1-50); intact hEGF accounted for one-third of the total materials recovered. Automated Edman degradation of each component for at least 10 cycles revealed a single amino acid sequence identical to that proposed for human beta-urogastrone. Similar immunoreactive hEGF components were observed in similar proportions in freshly voided urine, indicating that they were not artifacts of the purification process. Thus, multiple forms of fully biologically active hEGF (i.e., beta-urogastrone) can be relatively easily and efficiently purified from large volumes of human urine.

Comparison of human urine gastric inhibitor (HUGI) and bacterial endotoxin as inhibitors of acid secretion

In conscious cats with gastric fistulas, 10 micrograms . kg-1 of human urinary gastric inhibitor (HUGI) given as an intravenous bolus injection increased mean rectal temperature 1.4 degree C and inhibited mean gastrin-stimulated acid secretion by 64%. The sample of HUGI contained an amount of beta-hydroxymyristic acid corresponding to a 5% contamination of the HUGI with bacterial endotoxin. Injection of bacterial endotoxin in an amount corresponding to the beta-hydroxymyritic acid content of HUGI mimicked, both in magnitude and time course, the increase in body temperature and the inhibition of acid secretion produced by HUGI. We conclude that inhibition of acid secretion by HUGI may be due to the presence of an endotoxin-like contaminant.

The human urinary gastric inhibitor displays blood-group activity

The human urinary glycoprotein with gastric antisecretory activity displays a marked blood-group activity corresponding to the blood-group of the subject examined. Several studies exclude the possibility that the activity is due to contaminants.

Inhibition of gastric acid secretion by a glycoprotein isolated from human urine (human urinary gastric inhibitor)

The gastric antisecretory activity of an inhibitor newly isolated from human urine (Human Urinary Gastric Inhibitor or HUGI) has been studied. HUGI was given intravenously and its activity determined in the following test systems: gastric secretion in the rat with pyloric ligation; gastric secretion in the dog with a Heidenhain pouch stimulated with pentagastrin, histamine and a protein meal; acid secretion by the isolated gastric mucosa of the rat; gastrointestinal motility; bile flow and gall-bladder tone and arterial and venous blood pressure and heart rate. HUGI was found to have marked activity only in the pyloric-ligated rats and in the dogs with Heidenhain pouches stimulated by a protein meal. Particularly in the dog, HUGI (0.1 to 6.4 micrograms/kg, i.v) markedly inhibited gastric secretion, dose-dependently and without changing the plasma gastrin concentration. Negative results were obtained in the other tests, but these results serve to demonstrate that HUGI is an inhibitor well-differentiated from other glycoproteins or peptides with gastric antisecretory activity, such as urogastrone and GIP. The results obtained to date are not sufficient to allow the mechanism of action of HUGI to be defined.

Chemical and physical properties of the human urinary glycoprotein with gastric antisecretory activity

The chemical and physical properties of the high-molecular-weight glycoprotein (SO20, w = 8S; Ve=Vo on Sephadex G-200) with gastric antisecretory activity extracted from the urine of pregnant women were studied. Gel filtration in the presence of sodium dodecyl sulphate and sodium dodecyl sulphate/polyacrylamide-disc-gel electrophoresis indicated subunit mol.wts. of 16 000 +/- 1500 and 13 000 +/- 1000 respectively. Reaggregation of the subunits and partial recovery of the biological activity were observed on removal of the detergent. The partial C-terminal sequence was found to be Phe-Tyr-Leu-Val-OH, whereas glycine appears to be the N-terminal amino acid. The carbohydrate composition was examined; all galactosamine was found to be O-glycosidically linked to the polypeptide chain.