Procolipase is produced in the rat stomach--a novel source of enterostatin

Procolipase was identified in the stomach by in situ hybridisation. A strong autoradiographic labelling of chief cells was seen in the fundus region, declining more distally and being almost absent in antrum. There was no labelling seen in the intestine. Colipase activity was estimated in rat gastric juice following pentagastrin stimulation and was found to average 2 microM. Furthermore, enterostatin, the N-terminal pentapeptide of procolipase, has been identified in the rat gut and pancreas. Extracts from gastric mucosa, intestinal mucosa and pancreas were purified by gel filtration (Sephadex G25), ion-exchange chromatography (CM-Sepharose) and HPLC (C18 reverse phase). Using an ELISA assay with antibodies directed against enterostatin, two forms of the peptide were identified both in the gut and in the pancreas, with the amino-acid sequences APGPR and VPGPR, respectively. APGPR was found to be the predominant form of enterostatin, whereas only a small amount had the structure VPGPR. Enterostatin in the form of APGPR, when injected intracerebroventricularly in female Sprague-Dawley rats, significantly reduced high-fat food intake in a two-choice situation of low-fat (14% fat by energy) and high-fat (38% fat) food. It is concluded that procolipase is produced in the stomach and secreted into the gastric juice. This is also a novel source of enterostatin.

In vitro effects of ethanol on human gastric and pancreatic lipolytic activities/enzymes

BACKGROUND

Ethanol ingestion may disturb fat digestion and absorption by affecting gastric, intestinal, hepatic, and pancreatic functions. Involved mechanisms are not well understood. We examined in vitro ethanol effects on gastric and pancreatic lipolytic activity.

METHODS

Human gastric juice, pure gastric lipase, pancreatic lipase, colipase, carboxyl ester lipase, phospholipase A2, and duodenal contents were a) preincubated at 37 degrees C with ethanol (0-30%) and then assayed under normal conditions (pH-stat titration), or b) assayed in the presence of various ethanol concentrations (0-30%).

RESULTS

Ethanol reduced gastric and pancreatic lipolytic activities in a dose-dependent manner. The effect was more pronounced with alcohol present in the assay medium, with 5% ethanol reducing carboxyl ester lipase activity by 10%, gastric lipase activity by 20%, and pancreatic lipase activity by 46%. Colipase and phospholipase A2 activities were only slightly affected by ethanol.

CONCLUSIONS

Observed effects of ethanol on gastric and pancreatic lipase may be important when fat digestion is already impaired due to gastric, intestinal hepatic, and/or pancreatic diseases.

Inhibition of human pancreatic proteinases by mucus proteinase inhibitor, eglin c and aprotinin

The kinetic investigation of the inhibition of human pancreatic trypsin 1, trypsin 2 and chymotrypsin A by mucus proteinase inhibitor, eglin c and aprotinin reveals that (i) the first protein is a potent inhibitor of chymotrypsin A (kass. = 1.4 x 10(6) M-1.s-1, Ki = 71 pM) but forms loose complexes with trypsin 1 (Ki = 0.5 microM) and trypsin 2 (Ki = 18 nM), (ii) eglin c does not inhibit the two trypsins but forms a tight complex with chymotrypsin A (kass. = 3.3 x 10(6) M-1.s-1, Ki < 0.1 nM) and (iii) aprotinin is a potent inhibitor of trypsin 1 (kass. = 1 x 10(6) M-1.s-1, Ki < 0.2 nM) and trypsin 2 (kass. = 2.4 x 10(5) M-1.s-1, Ki < 1 nM) but forms a loose complex with chymotrypsin A (Ki = 0.17 microM). These data, together with those published previously on human pancreatic elastase, suggest that a cocktail of aprotinin + eglin c might be a better intensive-care drug for acute pancreatitis than aprotinin alone, because it will efficiently inhibit all four human pancreatic proteinases. On the other hand, human gastric juice inactivates mucus proteinase inhibitor by pepsin-mediated cleavage. This indicates that the fraction of mucus proteinase inhibitor that reaches the stomach following aerosol delivery to cystic fibrosis patients does not reach the duodenum in an active form and, therefore, does not aggravate the pancreatic insufficiency of these patients.

[Gastric juice acidity in gastric ulcer]

Gastric juice acidity was examined in 131 patients with gastric ulcer. In 31 (23.7%) patients it appeared to be high, in 57 (43.5%)-normal, in 42 (32.8%)-low. In 28.6% cases the pepsin concentration was high, in 26.5%-normal, in 44.9% - low. In elder patients, patients with cardial ulcer, plural and combined ulcers, big size ulcers, long-term ulcer anamnesis the rate of low acidity increases. Among patients with unsatisfactory results of conservative treatment 15.8% had high acidity and 38.7% low acidity. Low acidity is an unfavorable prognostic factor.

Interfacial binding of human gastric lipase to lipid monolayers, measured with an ELISA

Two sandwich enzyme linked immunosorbent assays (ELISA) were developed for evaluating the surface excess at the lipid/water interface of the human gastric lipase (HGL) and two anti-HGL monoclonal antibodies (mAbs). These assays were adapted to the monomolecular film technique used previously for measuring lipase kinetics. HGL and the two anti-HGL mAbs (4-3 and 218-13) were biotinylated without any significant loss of their biological activities occurring. They were further detected by ELISA using either anti-HGL or anti-mouse IgG polyclonal antibodies as specific captors before being revealed using a streptavidin--peroxidase conjugate as tracer. The detection limit was 25 and 85 pg in the case of HGL and mAb, respectively. By combining the above sandwich ELISA technique with the monomolecular film technique, it was possible for the first time to measure the enzymatic activity of HGL on 1,2-didecanoyl-sn-glycerol (dicaprin) monolayers as well as to determine the corresponding interfacial excess of the enzyme. The HGL turnover number increased steadily with the lipid packing. The specific activities determined on dicaprin films spread at 35 mN.m-1 were found to be in the range of the values measured under optimal bulk assay conditions, using tributyrin emulsion as a substrate [i.e., 1000 mumol/(min.mg of enzyme)]. At a given lipase concentration in the water subphase, the interfacial binding of HGL to the nonhydrolyzable egg yolk phosphatidylcholine (egg PC) monolayers was found to be 10 times lower than that in the case of dicaprin monolayers.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary fat modulates gastric lipase activity in healthy humans

The aim of this study was to determine whether the amount of dietary fat modulates the activity of gastric lipase in humans. Gastric juice was collected from six healthy subjects after 2-wk periods of either a high-fat (50% of energy as fat) or low-fat (25% of energy as fat) diet. The collection period lasted 2 h, the first hour under baseline conditions and the second hour after pentagastrin stimulation (6 micrograms/kg body wt). Gastric lipase and pepsin activities were quantitated at 15-min intervals and total enzyme outputs were calculated. Under baseline conditions there was a tendency for higher output of gastric lipase and pepsin after the high-fat diet than after the low-fat diet (gastric lipase: 745 compared with 446 U/h, pepsin: 107,677 compared with 78,505 U/h). The difference in output between diet groups was significant after pentagastrin stimulation (gastric lipase: 1323 compared with 875 U/h, pepsin: 191,751 compared with 128,961 U/h, for high-fat compared with low-fat diet, respectively, P < 0.05). This study is the first to report that a high-fat diet leads to an increase in the activity of gastric enzymes in humans.

Five human gastric aspartic proteinases: N-terminal amino acid sequences and amino acid composition

Human pepsin A consists of 4 or more isoenzymes (designated 1, 3a, 3b and 3c) one of which, pepsin 1, contains up to 50% carbohydrate moieties. The amino-acid composition and N-terminal sequence of pepsin 1 and the other isoforms have been determined and compared with data obtained for pepsin 3b and gastricsin (pepsin C or pepsin 5). Pepsins were isolated from penta-gastrin stimulated gastric juice using repetitive chromatography on DEAE-cellulose, or high performance ion-exchange chromatography. Sequencing was performed using automated solid-phase Edman degradation with a microsequence facility. The amino-acid compositions were similar for pepsins 1, 3a, b and c and the N-terminal sequences of pepsins 1, 3a and c, reported for the first time, were shown to be identical with that for pepsin 3b (the main component of pepsin A) although residue 28 was unassigned in pepsin 1. Residue 30 in all four isoenzymes is valine and we cannot confirm reports of major pepsins with leucine in this position. For gastricsin the sequence differed from the pepsin isoenzymes and in position 24 we find pro rather than ala as was first described. These observations suggest that pepsin 1 is identical to 3b or a mixture of 3a, 3b and 3c but not gastricsin. This data supports the hypotheses that the four pepsin isoenzymes are products of the same gene(s) but have undergone varying levels of post translational modification.

Lipolytic activity of bacterial lipase survives better than that of porcine lipase in human gastric and duodenal content

BACKGROUND/AIMS

Treatment of pancreatic steatorrhea with porcine lipase is unsatisfactory because it is rapidly denatured by acidic intraluminal conditions. The aim of this study was to determine if bacterial lipase is resistant to acid denaturation and is active in the presence of bile acids by comparing its stability with that of porcine lipase in gastric and duodenal juice obtained from six patients undergoing a cholecystokinin octapeptide pancreatic function test.

METHODS

After inactivating native lipolytic activity, both juices were altered to simulate fasting and postprandial conditions in normal patients and patients with pancreatic insufficiency. Gastric juice was adjusted to pH 2, 3, 4, or 6, duodenal juice to pH 4 or 6, and bile acid concentrations to 4 or 12 mmol/L. Nutrients were added to one half of the samples. Initial bacterial or porcine lipolytic concentrations were 25 or 250 U/mL. After a 1-hour incubation at 37 degrees C, lipolytic activity was remeasured.

RESULTS

In gastric juice, more bacterial lipolytic activity survived than porcine lipolytic activity at both concentrations in the absence of nutrients and at a concentration of 25 U/mL with nutrients (P < 0.05). In duodenal juice, more bacterial lipolytic activity survived than porcine activity at pH 4 under all test conditions (P < 0.05).

CONCLUSIONS

Bacterial lipolytic activity should survive better within the gastrointestinal lumen than porcine lipolytic activity and be more effective to treat steatorrhea.

Fatty acid and positional selectivities of gastric lipase from premature human infants: in vitro studies

Gastric lipase activity in aspirates from premature human infants was tested for fatty acid and positional selectivity using racemic diacid triacylglycerols (TG) as substrates. The resulting free fatty acids and monoacylglycerols (MG) were recovered and analyzed. Octanoic acid (8:0) and decanoic acid (10:0) were hydrolyzed with a preference of 61.5:1 and 2.4:1 compared to palmitic acid (16:0) from rac-16:0-8:0-8:0 and rac-16:0-10:0-10:0, respectively. The ratio of lauric acid (12:0) to oleic acid (18:1) hydrolyzed from rac-18:1-12:0-12:0 was 13:1. Myristic acid (14:0), 18:1 and linoleic acid (18:2) were released at similar rates. These data and the composition of the MG suggest that, in vitro, the lipase is selective for shorter chain fatty acids and for fatty acids on the primary positions of the TG backbone.

Subsite study of human pepsin in disease

The synthetic peptides AC-Glu-Phe-Phe (NO2)-Arg-amide (peptide VP) and AC-Ile-Glu-Phe-Phe (NO2)-Arg-amide (peptide VIP) are more readily hydrolyzed by human pepsin in gastric juice of patients of gastritis than those of duodenal ulcer and normal subjects. The kinetic parameters suggest that S3 subsite of the enzyme plays a role in the elevation of enzyme activity in gastric disease.

Phospholipase A2 activity in gastric juice from patients with active and H. pylori-eradicated healed duodenal ulcer

BACKGROUND

Despite the close association between gastric Helicobacter pylori infection and duodenal ulcer, little is known about how this organism may promote mucosal damage. A possibility might be that it produces, or induces the host to release, phospholipases that metabolize the protective layer of phospholipids.

METHODS

Aimed at determination of phospholipase A2 activity and the concentration of choline-containing phospholipids in gastric juice, aspirates were collected during gastroscopy in 38 consecutive referrals with either active (n = 19) or H. pylori-eradicated healed duodenal ulcer (n = 19).

RESULTS

Gastric juice phospholipase A2 activity was 3.1 times higher in active than in healed duodenal ulcers (P = 0.03). Concurrently, the concentration of choline-containing phospholipids in the group with active ulcers was less than half compared with the healed group (P = 0.02).

CONCLUSION

The results indicate that phospholipase A2 activity and the concentration of choline-containing phospholipids in gastric juice are related to H. pylori status and duodenal ulcer disease.

Adenosine deaminase, 5'-nucleotidase, xanthine oxidase, superoxide dismutase, and catalase activities in gastric juices from patients with gastric cancer, ulcer, and atrophic gastritis

Adenosine deaminase (ADA), 5'-Nucleotidase (5NT), Xanthine oxidase (XO), Cu-Zn Superoxide dismutase (SOD) and Catalase (CAT) activities were determined in gastric juices from patients with gastric cancer, ulcer, gastritis and from healthy subjects. Enzyme activities were given as units per ml gastric juice and units per mg protein in gastric juice. ADA, 5NT and XO activities were found lower and protein concentrations were found higher in the cancer group than controls. There was however no significant difference between Cu-Zn SOD activities of the cancer and control groups. In all groups including control one, we could not find catalase activities in most of the samples. On the other hand, ADA, 5NT activities and protein concentrations in the gastric juice were lower in the gastritis group than control group. In the ulcer group, we found higher Cu-Zn SOD and XO activities and lower 5NT activity and protein concentrations compared with control values. In an attempt to establish statistical correlations between mean enzyme activities, pH and protein concentrations in the gastric juices of the groups, we found noticeable intra and inter-correlations, which indicated possible relations between DNA and free radical metabolizing enzymes.

Tertiary amines as antagonists of both the luminal and cytosolic K(+)-site of gastric H,K-ATPase

Tertiary amines like imidazole and triallylamine lower the apparent affinity of K+ in the ATP hydrolysis reaction of pig gastric H,K-ATPase in a pH and amine concentration dependent way. The mechanism and sidedness of this effect was studied by analyzing the partial reactions of the enzyme in both leaky and ion-tight vesicles. In leaky vesicles Tris and Hepes had nearly no effect on the apparent Km for K+ in the ATPase reaction, but imidazole (Ki = 13 mM) and triallylamine (Ki = 1.6 mM) markedly decreased the K+ affinity. The steady-state ATP-phosphorylation level in the absence of K+ was not or only slightly affected by these compounds. The reduction of the ATP-phosphorylation level by K+, however, again depended on both the type and concentration of tertiary amine used. A comparable K(+)-amine antagonism was observed in the dephosphorylation reaction. In tightly sealed vesicles, where no activation of K+ at the luminal side could occur, K+ reduced the affinity for ATP in the phosphorylation reaction. Triallylamine counteracted this effect. The K(+)-activated p-nitrophenylphosphatase activity in these ion-tight vesicles also showed a K(+)-triallylamine antagonism. Inhibition of H,K-ATPase activity in these vesicles by triallylamine was immediate (with nigericin present in order to allow intravesicular K+ activation), suggesting the transmembrane feature of this inhibition. These results indicate that tertiary amines decrease the affinity for K+ at both luminal and cytosolic binding sites by interaction at the cytosolic side of the membrane. This results in shifts in the equilibrium of both the E1.H<==>E1.K transition and in the dephosphorylation reaction, E2-P-->E2.K.

Development of lipolytic activity in gastric aspirates from premature infants

Neonates, having little or no pancreatic lipase, would have a compromised ability to digest lipids if not for lingual and gastric lipases. To document the postnatal developmental profile of preduodenal lipase activity, 350 premature infants who were at various gestational ages and who had an orogastric tube had their gastric aspirates collected. Two hundred one infants had their gastric aspirates collected within 12 h after delivery. Serial collections were performed in 25 infants at various postnatal ages. Gastric aspirates collected from premature infants had a pH activity profile similar to that of lingual and gastric lipase but different from that of pancreatic lipase, indicating that their origin was from the tongue and/or stomach. Lipolytic activity and pH of these aspirates were quite variable, but no correlation was found between pH and enzyme activity. At birth, lipase activity was lower in the younger infants (< or = 26 weeks, n = 13). It increased to a peak at 30-32 weeks of gestational age and then declined to a lower level at term (> or = 40 weeks, n = 40). Postnatally, a composite plot of the serially collected aspirates also showed a predominant peak at 28-33 weeks of age. Comparison among siblings in twins (n = 12 pairs) and triplets (n = 3) showed great variations in their lipolytic activities, suggesting that the hereditary factor is not a major determinant. Various combinations of antibiotic medications (ampicillin, cefotaxime, gentamicin, and vancomycin) and drugs (dexamethasone, heparin, furosemide, phenobarbital, albumin, and vitamin K) apparently had no effect on the level and development of gastric lipolytic activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification of human gastric lipase by immunoaffinity and quantification of this enzyme in the duodenal contents using a new ELISA procedure

Human gastric lipase (HGL) is the first lipolytic enzyme involved in the digestion of dietary lipids along the gastrointestinal tract. We describe an improved procedure for isolating the enzyme using immunoaffinity chromatography in combination with ion-exchange chromatography. The purified enzyme, showing a single band on SDS-PAGE, expressed a specific activity of 1000 U/mg using tributyrin as the substrate. We also describe a specific enzyme-linked immunosorbent assay (ELISA) procedure for measuring duodenal HGL levels. The ELISA was performed using an anti-HGL polyclonal antibody (pAb) as the captor antibody and a biotinylated monoclonal antibody (mAb) as the detector antibody. With the double sandwich ELISA technique, HGL in the range of 1-60 ng/ml was measured in less than 5 h. Identical HGL concentrations were obtained using the above ELISA procedure when compared to those based on the enzymatic activity using the potentiometric method (correlation coefficient: r = 0.95). No significant interference from other duodenal components was observed, as proved by the quantitative HGL determinations performed on intestinal samples.

Purification and characterization of guinea pig gastric phospholipase A2 of the pancreatic type

Guinea pig gastric mucosa and juice contained exceptionally high phospholipase-A2 activity, whereas the activity in the pancreas was only minimal. Phospholipases A2 were purified to homogeneity from these three tissues. Structural evidence, including the sequence of the NH2-terminal 41 residues, the amino-acid composition and the molecular mass (13902 +/- 3 Da) determined accurately by mass spectrometry, showed that the gastric mucosa enzyme belongs to the pancreatic type. An unique feature of the sequence is the substitution of Phe for the hitherto invariant Tyr28 in the calcium-binding loop of pancreatic phospholipases A2. The affinity of the guinea pig enzyme for Ca2+ in the presence of substrate was, however, identical to that of the rat enzyme with Tyr28, suggesting the interaction of a phenolic hydroxyl group of the Tyr with its neighboring residues is not significantly linked to the binding of Ca2+. The NH2-terminal sequences and immunochemical properties of the enzymes purified from the gastric juice and pancreas were identical to those of the gastric mucosa enzyme. The distribution of cells immunoreactive with anti-(gastric PLA2) immunoglobulin in the stomach was quite similar to that of the chief cells. Unlike in pancreas of other animals, the prophospholipase A2 was not detectable in gastric mucosa or juice homogenates treated with diisopropyl fluorophosphate or in column effluents during purification under acidic conditions. An appreciable prophospholipase-A2-activating activity was not detectable in gastric mucosa extracts at low pH relevant to gastric juice, using rat prophospholipase A2 as substrate. This opposes the activation of secreted proenzyme in the gastric juice.

Amino acid sequence of alkaliphilic serine protease from silkworm, Bombyx mori, larval digestive juice

Alkaliphilic protease, P-IIc, from silkworm, Bombyx mori, larval midgut digestive juice consists of 232 amino acids. It has a catalytic triad, Asp-His-Ser, invariably found in a serine protease. A shift of optimal pH value towards the alkaline side diminished at mu = 1.0. This suggests the existence of an electrostatic interaction that affects the proteolytic activity. The higher Arg content may be responsible for this phenomenon. Two cysteine residues probably exist unpaired in a novel position among serine proteases.

Assay of gastricsin and individual pepsins in human gastric juice

AIMS

To develop and validate an analytical procedure for the quantitation of pepsins and gastricsin in human gastric juice and to assess its potential in a controlled gastric secretory study.

METHODS

High performance ion-exchange chromatography was used to separate human pepsin 1, 3a, 3b, 3c and gastricsin from gastric juice. Computed chromatographic areas for each enzyme were quantified by relation to a known amount of a secondary standard porcine pepsin. The assay procedure was validated by recovery and analytical precision studies. Gastric secretions after pentagastrin and insulin stimulation from 10 patients with portal hypertension were used to assess the potential of the analytical procedure.

RESULTS

The assay precision varied from 1.5 to 9.0% within batch and 7.5 to 18.1% between batch, with about 100% recoveries of porcine pepsin A from human gastric juice over the assay range 0.025-0.5 mg/ml. A fourfold increase in combined pepsin and gastricsin concentration was observed following pentagastrin and insulin stimulation. The mean percentage content of pepsins 3a, 3b, 3c, and 1 in non-stimulated gastric juice were 4%, 72%, 12% and 1.4%, respectively, and did not change significantly after gastric stimulation. An approximate doubling of the percentage of gastricsin (10% to 20%) relative to the pepsins was observed, however, after both insulin and pentagastrin stimulation.

CONCLUSIONS

This procedure for quantifying individual human pepsins and gastricsin in gastric juice is simple and reliable. It may be of considerable importance in determining the mechanisms involved in the control and secretion of these digestive enzymes in man, including the effect of anti-ulcer drugs and our understanding of the pathophysiology of peptic ulcer disease.

Effect of dexamethasone on the peptic activity of gastric lumen and mucosa

Dexamethasone (9 alpha-fluoro-16 alpha methyl-11 beta,17 alpha,21-trihydroxy-1,4-pregnadiene-3,20-dione-21-phosphate), a synthetic glucocorticoid, has a dual role on pepsinogen content of the gastric lumen and mucosa as measured by its peptic activity. Following stimulation the luminal peptic activity gradually decreases after 6 hr, then returns to basal levels at 18 hr and by 24 hr is inhibited by 50%. The luminal peptic activity induced by the secretory compound mercaptomethylimidazole (MMI) is also decreased. Dexamethasone effect on both basal and MMI-induced peptic activity can be reproduced by cycloheximide or puromycin, translational blockers of protein synthesis. This drug also has an independent time and dose-dependent inhibitory effect on gastric mucosal peptic activity which does not correlate with increased peptic activity of the lumen. Dexamethasone appears to be more effective than hydrocortisone and corticosterone in inhibiting the basal peptic activity of both lumen and mucosa. The inhibitory effect of this drug on tissue peptic activity is not mediated through induction of any inhibitory protein as evidenced by the insensitivity of the effect to actinomycin D. Studies on [14C]phenylalanine incorporation into gastric protein indicate that the effect of dexamethasone on tissue pepsinogen content is not due to a generalized block of protein synthesis.

Epitope mapping and immunoinactivation of human gastric lipase using five monoclonal antibodies

Five monoclonal antibodies (mAb) directed against human gastric lipase (HGL) have been produced by hybridization of myeloma cells with spleen cells of BALB/c immunized mice. All these mAb belong to the IgG1 class with a kappa light chain. The effects of these mAb on the enzymic activity of HGL were studied and used to define three classes of antibodies, depending upon their immunoinactivation properties. As determined by ELISA and immunoinactivation studies, four overlapping epitopes were found to be part of the functional sites of the enzyme. The mAb appear to be suitable probes for studying the lipid binding and catalytic domains of HGL. The results of the ELISA additivity test were used to describe tentatively the epitopes of HGL in terms of a schematic spatial map.

[The diagnostic accuracy of gastric urease activity for Helicobacter pylori]

The diagnostic accuracy of gastric urease activity for Helicobacter pylori (HP) infection were studied in 98 patients with peptic ulcer, gastritis and chronic renal failure. Gastric aspirates were analyzed for urea nitrogen and ammonia. Urease activity was calculated as the ratio of gastric ammonia to sum of gastric urea nitrogen and ammonia. Gold standard assessments to HP infection were rapid urease test, histology and/or culture. The results showed that the values of urease activity in patients with HP infection higher than that in patients without HP infection. This were further assessed by eradication of HP. Sixteen patients with HP infection were treated with DeNol 330 mg/day for 4 weeks. HP was eradicated in 8/16 patients. In those cases urease activity reduced (P < 0.05). If taken 0.31 as the cut-off index of urease activity to diagnosis HP infection, the sensitivity, specificity and accuracy were 95%, 84%, 93% respectively and were not affected by blood urea nitrogen.

Assay of sialyltransferase activity by reversed-phase ion-pair high-performance liquid chromatography

Sialyltransferases (CMP-N-acetylneuraminic acid:glycoprotein sialyltransferases, EC 2.4.99.1) are involved in the transfer of a sialic acid moiety from CMP-N-acetylneuraminic acid (CMP-NeuAc) to an oligosaccharide side-chain of an acceptor, asialoglycoprotein (AGP), according to the following reaction: CMP-NeuAc + AGP----NeuAc-O-AGP + CMP. This enzyme occurs in elevated levels in the sera of patients with a wide variety of neoplastic diseases and its assay might be useful in monitoring treatment. Radioactive CMP-NeuAc has been used in assays and the radioactive sialylated product separated and counted by liquid scintillation spectrometry. This study shows that a simple, rapid, non-radiochemically based high-performance liquid chromatographic method developed for the analysis of CMP-sialic acid synthetase can be used for the quantitation of sialyltransferase activity by monitoring simultaneously the utilization of CMP-NeuAc and the release of CMP. We describe the application of this method to assay of commercially available sialyltransferase activity and to activities from synovial, ascites and gastric fluids.

[Clinical application of beta-glucuronidase (beta-GCD) assay in the diagnosis of malignant tumors--analysis of 743 cases]

Chromatometric assay of beta-GCD in the urine, gastric juice and saliva was conducted in 743 subjects. In the urine of 104 normal persons, 5 (4.8%) were beta-GCD positive. In the urine of 35 urinary bladder cancer patients, 20 (57.1%) were positive. beta-GCD content was very low in the gastric juice and saliva of normal subjects, giving a positivity of 0%. But it was high in the gastric juice of stomach cancer patients, giving a positive rate of 83.3%. The positivities in the saliva of stomach cancer and malignant ovarian tumor patients were both 62.2% which was higher than that of patients suffering from other malignancies or benign tumors. beta-GCD assay is simple, stable and is valid in the diagnosis of stomach cancer and ovarian malignancies. The mechanism of beta-GCD elevation and its relation to metastasis are discussed.

Effect of pancreatic phospholipase A2 and gastric lipase on the action of pancreatic carboxyl ester lipase against lipid substrates in vitro

Preincubation of a triolein/phospholipid/cholesteryl oleate-emulsion in vitro with either pancreatic phospholipase A2 (PLA2) or gastric lipase (GL) resulted in hydrolysis (measured by pH-stat-titration) of cholesteryl [3H]oleate only after human pancreatic carboxyl ester lipase (CEL) was added to the system. No appreciable hydrolysis was observed when CEL was added alone. Consequently, a concerted action either of PLA2 and CEL or of GL and CEL made the substrate cholesteryl oleate available for hydrolysis by CEL. This was the case when cholesteryl oleate was solubilised in a phospholipid-stabilised triglyceride emulsion, which is the physico-chemical form in which the major part of dietary cholesteryl esters are presented to the gastro-intestinal tract of man.

Acute gastric mucosal injury induced by toxins from Tityus serrulatus scorpion venom: a novel experimental model in the rat

The effect of a partially purified fraction (T1) and toxin gamma purified from Tityus serrulatus scorpion venom, on gastric mucosa were investigated in anesthetized rats. The animals were injected i.v. with the T1 fraction (37.5 micrograms/100 g) or with saline and 60 min later were sacrificed and the stomachs resected. The gastric juice was measured and stereoscopic examination of the stomachs made. In animals injected with the T1 fraction there was an increase in volume, acidity and pepsin output of rat stomach. The T1 fraction also induced acute gastric injuries in the glandular mucosa, consisting of circular or linear ulcers, and punctiform lesions. Intravenous injection of 20 micrograms/100 g of a pure toxin obtained from Tityus serrulatus scorpion venom (toxin gamma) also induced similar lesions in the rat stomach. Our data indicate that the injection of T1 fraction or toxin gamma are good models to induce acute gastric ulcers in a short period of time in anesthetized rats.

Stereoselectivity of lipases. II. Stereoselective hydrolysis of triglycerides by gastric and pancreatic lipases

In the present study, porcine pancreatic lipase, rabbit gastric lipase, and human gastric lipase stereospecificity toward chemically alike, but sterically nonequivalent ester groups within one single triglyceride molecule was investigated. Lipolysis reactions were carried out on synthetic trioctanoin or triolein, which are homogenous, prochiral triglycerides, chosen as models for physiological lipase substrates. Diglyceride mixtures resulting from lipolysis were derivatized with optically active R-(+)-1-phenylethylisocyanate, to give diastereomeric carbamate mixtures, which were further separated by high performance liquid chromatography. Resolution of diastereomeric carbamates gave enantiomeric excess values, which reflect the lipases stereobias and clearly demonstrate the existence of a stereopreference by both gastric lipases for the sn-3 position. The stereoselectivity of human and rabbit gastric lipases, expressed as the enantiomeric excess percentage, was 54% and 70% for trioctanoin and 74% and 47% for triolein, respectively. The corresponding values with porcine pancreatic lipase were 3% in the case of trioctanoin and 8% in that of triolein. It is worth noting that rabbit gastric lipase, unlike human gastric lipase, became more stereoselective for the triglyceride with shorter acyl chains (trioctanoin). This is one of the most striking catalytic differences observed between these two gastric lipases.

Stereoselectivity of lipases. I. Hydrolysis of enantiomeric glyceride analogues by gastric and pancreatic lipases, a kinetic study using the monomolecular film technique

In the present study, porcine pancreatic lipase, rabbit gastric lipase, and human gastric lipase stereospecificity toward enantiomeric glyceride derivatives was kinetically investigated using the monomolecular film technique. Pseudoglycerides such as enantiomeric 1(3)-alkyl-2,3(1,2)-diacyl-sn-glycerol, enantiomeric 1(3)-alkyl-2-acyl-sn-glycerol, or enantiomeric 1(3)-acyl-2-acylamino-2-deoxy-sn-glycerol were synthesized in order to assess the lipase stereoselectivity during the hydrolysis of either the primary or the secondary ester position of these glycerides analogues. The cleaved acyl moiety was the same in both enantiomers, thereby excluding the possibility of effects occurring due to fatty acid specificity. We observed a porcine pancreatic lipase sn-3 stereoselectivity when using the enantiomeric 1(3)-alkyl-2-acylamino-2-deoxy-sn-glycerol (diglyceride analogue) which contrasted with the lack of stereoselectivity observed when using the enantiomeric 1(3)-alkyl-2,3(1,2)-diacyl-sn-glycerol (triglyceride analogue). The gastric lipases, in contrast to the pancreatic lipase, preferentially catalyze the hydrolysis of the primary sn-3 ester bond of the enantiomeric monoakyl-diacyl pair tested. From these kinetic data, high hydrolysis rates and no chiral discrimination were observed in the case of rabbit gastric lipase, whereas low rates and a clear chiral discrimination was noticed in the case of human gastric lipase during hydrolysis of the acyl chain from the secondary ester bond of 1(3)-alkyl-2-acyl enantiomers. It is particularly obvious that in the case of human gastric lipase decreasing the lipid packing increases the lipase sn-3 stereopreference during hydrolysis of the primary ester bond of the enantiomeric 2-acylamino derivatives (diglyceride analogue).

Inhibition of gastric pepsin secretion by peripherally or centrally injected interleukin-1 in rats

The present study was carried out to investigate the effects of Interleukin-1 (IL-1) on gastric pepsin secretion in conscious pylorus-ligated rats. The intraperitoneal (ip) injection of IL-1 resulted in a dose-related inhibition of gastric pepsin output. The intracerebroventricular (icv) injection of IL-1 similarly reduced pepsin secretion at 100 times smaller doses than ip IL-1, suggesting that this inhibitory action of IL-1 is mediated by the central nervous system (CNS). In addition, it was found that the antisecretory action of IL-1, both peripherally and centrally administered, lasted throughout the periods observed (2 hr through 8 hr after injection). These results strongly indicate that IL-1 is involved in the CNS regulation of gastric secretion, especially under certain pathophysiological conditions which activate the immune system to release various cytokines including IL-1.

[Superoxide dismutase activity of digestive secretions]

A superoxide dismutase (SOD) activity in saliva and gastric juice has been revealed using the NBT reduction and adrenaline autooxidation assays. This activity in saliva is induced mainly by enzymic mechanisms, whereas in gastric juice--by nonenzymic mechanisms. The gel chromatographic analysis of saliva has demonstrated the presence of several SOD isoenzymes. Nonenzymic mechanisms of the SOD activity in gastric juice involve the ionic activity of H+, Cu2+ and that of reduced glutathione. The SOD activity in gastric juice can be decreased by adding antacids and Fe ions. The effect of Fe3+ is found to be different depending on the methods of the SOD activity evaluation. Such metal-chelating agents as histidine and organic acids increase the SOD activity in gastric juice.

Purification and characterization of a digestive cysteine proteinase from the American lobster (Homarus americanus)

A new cysteine proteinase was isolated from the digestive juice of the American lobster (Homarus americanus). The enzyme was purified by a combination of affinity and ion-exchange chromatography and gel filtration. The cysteine proteinase accounted for 80% of the proteolytic activity in the lumen of the hepatopancreas. The most potent heavy-metal inhibitors were Hg, Cu, and Ag ions. Inhibition by organic proteinase inhibitors, including E-64 [L-trans-epoxysuccinyl-leucylamido-(4-guanidino)butane] and activation of the enzyme by 2-mercaptoethanol and dithiothreitol are characteristic of cysteine proteinases. Several similarities to papain are noted and include the N-terminal sequence, of which 22 of the first 28 amino acids are identical. Some notable differences are the higher Mr of 28,000 compared with 23,350 for papain, and the low isoelectric point (pI 4.5) of the lobster enzyme. The effects of pH and temperature on catalytic activity of the lobster proteinase were studied with benzyloxycarbonylalanine p-nitrophenyl ester as the substrate. The kcat./Km value was effectively temperature-independent between 10 and 60 degrees C. The pH-activity profile for the lobster enzyme revealed four apparent protonation states, of which only two are active.

Effects of 12-sulfodehydroabietic acid monosodium salt (TA-2711), a new anti-ulcer agent, on gastric secretion and experimental ulcers in rats

Effects of 12-sulfodehydroabietic acid monosodium salt (TA-2711), a new anti-ulcer agent, on gastric secretion and experimental ulcers were investigated in rats. Oral administration of TA-2711 at doses of 25 to 100 mg/kg immediately after pyloric ligation markedly reduced pepsin activity and slightly lowered acid concentration without affecting the volume of gastric juice. Addition of TA-2711 (0.25-16 mg/ml) directly to gastric juice also reduced pepsin activity in vitro. Oral TA-2711 dose-relatedly inhibited the formation of pylorus-ligated ulcers (50-200 mg/kg), aspirin-induced gastric erosions (25-100 mg/kg) and cysteamine-induced duodenal ulcers (100-800 mg/kg). In addition, this drug prevented both the formation of gastric lesions (6.3-100 mg/kg, p.o.) and the fall in gastric potential difference (100 mg/kg, p.o.) induced by ethanol. The preventive effect against ethanol-induced lesions was suppressed by pretreatment with indomethacin (10 mg/kg, s.c.). Intravenous dosing of TA-2711 (10-100 mg/kg) never produced such effects on ethanol-induced lesions and pepsin activity as observed by oral administration. These results indicate that TA-2711 exerts its anti-ulcer effect by a local action, and it is suggested that both reduction of pepsin activity and a mucosal prostaglandin-mediated process are involved in the anti-ulcer action of TA-2711.

Improved separation of human pepsins from gastric juice by high-performance ion-exchange chromatography

A simple and precise separative procedure can now be used to isolate individual pepsins from gastric juice, and by measurement of the protein absorbance at 280 nm enable their direct quantitation. This will facilitate the study of pepsin secretion, particularly in patients with peptic ulcer disease.

The effect of tripotassium dicitrato bismuthate on pepsin activity

We have studied the effect of tripotassium dicitrato bismuthate on the peptic activity of gastric juice, both basal and pentagastrin-stimulated, from five healthy volunteers using porcine pepsin solution as a control. Tripotassium dicitrato bismuthate showed no inhibition of the proteolytic activity of either the pure porcine or the human pepsin in the gastric juice. The ulcer healing efficacy of tripotassium dicitrato bismuthate is unlikely to be related to a gastric anti-protease effect.

Human gastric lipase. The N-terminal tetrapeptide is essential for lipid binding and lipase activity

Human gastric lipase subjected to limited tryptic proteolysis lost its ability to hydrolyze emulsified long-chain triacylglycerol. Activity against a water-soluble substrate was however retained, indicating that proteolysis did not affect the active site. Sequence analysis revealed that trypsin specifically cleaved the linkage between lysine-4 and leucine-5. This cleavage rendered the enzyme unable to bind to emulsified triacylglycerol particles, e.g. human milk fat globules. We suggest that the N-terminal tetrapeptide, in particular lysine-4, is essential for the binding of human gastric lipase to lipid/water interfaces, and hence, for its physiological function.

Determination of the pepsin activity in human gastric juice, using defined oligopeptides as substrates

Different methods for the determination of pepsin activity in human gastric juice, using defined oligopeptides as substrates, were investigated. N-Acetyl-L-phenylalanyl-L-3,5-diiodotyrosine and tripeptides like benzyloxycarbonyl-L-histidyl-L-phenylalanyl-L-tryptophan ethyl ester, benzyloxycarbonyl-L-histidyl-L-phenylalanyl-L-tyrosine ethyl ester, or benzyloxycarbonyl-L-histidyl-L-4-nitrophenylalanyl-L-phenylalanine methyl ester lead to only small absorption changes in the direct measurement of pepsin activity. Suitable substrates were shown to be the hexapeptide, L-leucyl-L-seryl-L-4-nitrophenylalanyl-L-norleucyl-L-alanyl-L- leucine-methyl ester and the octapeptide, L-prolyl-L-histidyl-L-leucyl-L-seryl-L-4-nitrophenylalanyl-L-norleucyl-L -alanyl-L-leucine methyl ester. Hydrolysis of these peptides can be measured continuously, using a spectral line photometer at 313 nm. Optimal test conditions and kinetic constants for substrate cleavage by pepsin in solution and by human gastric juice were determined.

A novel nonpeptidic, orally active renin inhibitor

BW-175 is a newly synthesized renin inhibitor which is a nonpeptidic, norleucine analog. Its IC50 values for renin activity in human, squirrel monkey, marmoset, dog, hog, rabbit and rat plasma were 3.3, 6.6, 2.4, 42, 110, 86 and 3500 nM, respectively, and 26 microM for cathepsin D. Pepsin and angiotensin converting enzyme were hardly inhibited at 10(-4) M. BW-175 showed an oral bioavailability of 2.8% at 10 mg/kg and 9.7% at 30 mg/kg in rats. In normotensive, furosemide-treated high-renin marmosets, BW-175 (30 mg/kg p.o.) caused an intensive reduction in plasma renin activity and plasma angiotensin I formation, associated with a reduction in systolic blood pressure of 10-20 mm Hg for 2 hours.

Role of a sulfhydryl group in gastric lipases. A binding study using the monomolecular-film technique

Native human and rabbit gastric lipases (HGL and RGL, respectively) were inactivated after modification of one sulfhydryl group/enzyme molecule. HGL and RGL were covalently labeled using 5,5'-dithiobis(2-nitro-[14C]benzoic acid) and the interaction of 2-nitro-5-thio-[14C]benzoic-acid-labeled lipases ([14C]Nbs-lipases) with monomolecular lipid films was investigated. Our results show that [14C]Nbs-lipases bind to lipid films as efficiently as native HGL or RGL. The critical surface pressure pi c and the maximal surface pressure (delta pi max) of [14C]Nbs-lipases were enhanced in comparison with those of native RGL and HGL. These changes in behavior were probably due to an increase in hydrophobicity brought about, directly or indirectly, by the binding of the Nbs radical. This chemical modification thus blocks the hydrolysis site and reinforces the hydrophobic character of the gastric lipases.

Immunopharmacological studies on Picrorhiza kurroa Royle ex Benth. Part VI: Effect on anaphylactic activation events in rat peritoneal mast cells

Mechanism of inhibition of mast cell anaphylaxis by P. kurroa-extract (PK) treatment in rats was investigated. Mast cell-IgE binding, assessed from induction of passive sensitization, was not affected. Calcium-independent early activation events in mast cell anaphylaxis indicated on inhibitory influence of PK-treatment. Inhibition of membrane-protease release by PK-treatment was suggested by study of gastric secretion and exhibition of saturable synergism with Di-isopropyl fluoro phosphate on inhibition of anaphylactic degranulation. pH-independence of mast cell stabilizing effect negates any PK-influence on phospholipid transmethylation. The results complement findings of earlier studies on indirect effects of PK through alteration of membrane structure/function.

Hydrolysis of fluorescent pyrenetriacylglycerols by lipases from human stomach and gastric juice

Fluorescent triacylglycerols containing pyrenedecanoic (P10) and pyrenebutanoic (P4) acids were synthesized and their hydrolysis by lipases from human gastric juice and stomach homogenate was investigated. The existence in stomach homogenate of four different lipolytic enzymes hydrolyzing fluorescent triacylglycerols is suggested by the comparison of various enzymatic properties: acyl chain length specificity, heat inactivation and effect of detergents (Triton X-100 and taurocholate), serum albumin, diethyl-para-nitrophenyl phosphate (E600) and other inhibitors. (1) The acid pH4-lipase hydrolyzes P10-triacylglycerols but not P4-triacylglycerol and exhibited the characteristic properties of the lysosomal lipase: the maximal activating effect of detergents occurs at relatively high concentrations (the substrate/detergent optimal molar ratios were 1:5 and 1:25 for triacylglycerols/taurocholate and triacylglycerols/Triton X-100, respectively); its activity was strongly inhibited by para-chloromercuribenzoate (2.5 mmol/l), but was not significantly affected by serum albumin and E600 (10(-2) mmol/l). (2) The neutral pH7-lipase hydrolyzes P10-triacylglycerols but not P4-triacylglycerol. It is resistant to E600 and heat-stable, similarly to the acid pH4-lipase, but it is well discriminated from the acid enzyme by its substrate/detergent optimal molar ratios (1:2 and 1:3 for triacylglycerols/taurocholate and triacylglycerols/Triton X-100, respectively), whereas higher detergent concentrations, optimal for the acid lipase, are strongly inhibitory for the neutral enzyme. (3) The pH5-lipase present in gastric juice as well as in stomach homogenate exhibited properties obviously discriminating it from the other lipolytic enzymes from stomach homogenate: broad substrate specificity for P10- as well as P4-triacylglycerols, activation by low concentrations of amphiphiles (with optimal ratios triacylglycerols/taurocholate, triacylglycerols/taurocholate and triacylglycerols/phosphatidylcholine around 1:1, 1:3 and 1:0.1, respectively), heat-lability, strong activation by serum albumin and inhibition by E600 (10(-2) mmol/l). This pH5-lipase is the sole lipolytic enzyme present in gastric juice and is probably identical with the well-known 'gastric' lipase. (4) A pH7.5-enzyme is characterized by its specificity for P4-triacylglycerols, its heat-lability at 50 degrees C and its strong inhibition by E600 (10(-2) mmol/l).

Human gastric lipase. Effects of fatty acid and bovine serum albumin on in vitro activity

Lipase activity was determined in gastric juice obtained from newborn babies who were fed formula milk (180 ml/kg/day). Samples of gastric juice collected 3 h after a feed were pooled and incubated with bovine serum albumin (BSA). The incubation mixtures containing milk fatty acids (750 nmol/tube) and BSA (0-5%) showed maximal lipase activity (as measured by the liberation of radiolabelled fatty acid from radiolabelled triglyceride) with 1.87% BSA in the first 60 min, but at subsequent time intervals higher enzyme activities were observed with 2.5 and 5% BSA. After extracting milk fatty acids from gastric juice the effects of BSA and sodium oleate on lipase activity were studied. The addition of BSA appeared to inhibit the enzyme, but when sodium oleate was included in the incubating system there was either stimulation or inhibition of lipase activity. A dual effect of BSA (i.e. stimulatory or inhibitory) was observed depending on the relative amounts of BSA and fatty acid present in the incubation tube. It is suggested that 1.87-5% is the optimum concentration range of BSA for the determination of lipase activity in gastric juice, in the presence of 250-500 nmol of fatty acid.

[Assessment of cholesterol esterase activity in the duodenal contents of man]

In 20 healthy patients the cholesterol esterase activity in duodenal content was examined. The cholesterol ether of o-coumaric acid was used as a substrate. Increase of the cholesterol esterase activity was noted after stimulation of pancreozymin and secretin. The cholesterol esterase concentration in duodenal content changes in more wide range than the index of the output. The cholesterol esterase output is the most significant informative index. There is not any cholesterol esterase activity in bile, gastric juice and saliva. The results obtained have shown that the main part of the estimated cholesterol esterase activity has a pancreatic base. The investigation of the cholesterol esterase activity in duodenal content may be used in the study of the exocrine function of pancreas.