A new, highly sensitive and specific assay for chymotrypsin

Stability of desmopressin loaded in liposomes

Desmopressin-containing liposome formulations have been developed for intranasal administration previously. Positively charged liposomes were found to be an efficient delivery system for desmopressin. In this study, stability of the loaded desmopressin in positively charged liposomes was further investigated. Comparison of the stability of desmopressin in solution and liposomes was made. Degradation of desmopressin was shown to follow a pseudo-first-order reaction. Degradation of desmopressin in both solution and liposomes demonstrated the same kinetic behavior and exhibited no significant difference in half-lives. Similar v-shape pH-rate profile was found for desmopressin degradation in solution and liposomes. At pH 4.0, the inflection point of the v-shape pH-rate curve, the reaction rate of desmopressin was lowest and the stability was greatest. The stability of lipid ingredients of dioleoylphosphatidylcholine (DOPC), cholesterol (C), and stearylamine (S) in the liposome dispersion at pH 4.0 was studied. Results demonstrated that DOPC, C, and S were relatively stable in the liposome structure when formulated with desmopressin. The degradation of desmopressin in solution and liposomes in the presence of alpha-chymotrypsin was investigated. A longer half-life for desmopressin in liposomes than in solution was observed. It was suggested that desmopressin was protected by the liposomes against alpha-chymotrypsin digestion.

The use of inhibitory agents to overcome the enzymatic barrier to perorally administered therapeutic peptides and proteins

The peroral administration of peptide drugs is a major challenge to pharmaceutical science. In order to provide a sufficient bioavailability of these therapeutic agents after oral dosing, several barriers encountered with the gastrointestinal (GI) tract have to be overcome by a suitable galenic. One of these barriers is caused by proteolytic enzymes, leading to a severe presystemic degradation in the GI tract. Besides some other strategies to overcome the so-called enzymatic barrier, the use of inhibitory agents has gained considerable scientific interest, as various in vivo studies could demonstrate a significantly improved bioavailability of therapeutic peptides and proteins, due to the co-administration of such excipients. In vitro techniques to evaluate the actual potential of inhibitory agents incubation with pure proteases, freshly collected gastric or intestinal fluids, mucosal homogenates, brush border vesicles and freshly excised mucosa. In situ techniques are based on single-pass perfusion studies cannulating different intestinal segments and determining the amount of undegraded model drug in perfusion solutions or blood. For in vivo studies, insulin is mostly used as a model drug, offering the advantage of a well-established method to evaluate the biological response after oral dosing by determining the decrease in blood glucose level. Generally, inhibitory agents can be divided into: inhibitors which are not based on amino acids (I), such as p-aminobenzamidine, FK-448 and camostat mesilate; amino acids and modified amino acids (II), such acid derivatives; peptides and modified peptides (III), e.g. bacitracin, antipain, chymostatin and amastatin; and polypeptide protease inhibitors (IV), e.g. aprotinin, Bowman-Birk inhibitor and soybean trypsin inhibitor. Furthermore, complexing agents and some mucoadhesive polymers also display enzyme inhibitory activity. Drawbacks of inhibitory agents, such the risk of toxic side effects or high production costs, might be excluded by the development of advanced drug delivery systems. Initial steps in this direction can be seen in the development of delivery system containing mucoadhesive polymers providing an intimate contact to the mucosa, thereby reducing the drug degradation between delivery system and absorbing membrane, controlled release systems which provide a simultaneous release of drug and inhibitor and in the immobilisation of enzyme inhibitors on delivery systems.

Elastase 1 and chymotrypsin B in pancreatic juice and feces

A chymotrypsin-like protease was detected along with elastase 1 in pancreatic secretion and stool. This enzyme was isolated from necrobiotic human pancreas, purified, partially characterized and designated as chymotrypsin B. Quantitative studies by rocket immunoelectrophoresis indicated that neither elastase 1 nor chymotrypsin B was degraded during intestinal passage. On the basis of a clinical study, both enzymes were found to reflect pancreatic function.

A possible zymogen self-destruct mechanism preventing pancreatic autodigestion

Incubation at 37 degrees C of human cationic trypsinogen purified by PAGE electrophoresis, results in development of proteolytic activity (enzyme Y) capable of rapidly degrading cationic and anionic trypsinogens to inert products. Enzyme Y appears to be a serine protease with a molecular weight of about 20,000 daltons and is different from any of the known pancreatic enzymes. The active enzyme may be derived from trypsinogen itself or a hitherto unrecognized precursor contaminating the trypsinogen fraction used in this work. Appearance of enzyme Y activity seems to be associated with the presence of traces of free trypsin. Enzyme Y possesses insignificant or no activity when tested with a variety of synthetic trypsin, chymotrypsin and other protease substrates. It is not inactivated by the specific trypsin and chymotrypsin inhibitors TLCK and TPCK, but its activity is reduced gradually by increasing concentrations of pancreatic secretory trypsin inhibitor. Ca2+ concentrations greater than 3 mM strongly inhibit enzyme Y, and diisopropylfluorophosphate completely inactivates it. The enzyme is stable when incubated at pH 1.9 and 37 degrees C for 30 min and its activity is not abolished by treatment with Hg2+. When added to pancreatic juice with low inhibitor content it causes rapid inactivation of zymogens without significant release of active enzymes or reduction of pancreatic trypsin inhibitor. Its physiological role may be perceived as a second line of defense against premature intrapancreatic activation of zymogens. Enzyme Y activity may be generated when trypsin inhibitor, the first line of defense, is sufficiently depleted by complex formation with inappropriately released trypsin to permit dissociation of a small amount of trypsin from this complex. This in turn may lead to activation of enzyme Y and inactivation of the zymogens of pancreatic proteases.

Elevated serum chymotrypsin levels in a patient with junctional epidermolysis bullosa. Normalization after UVB therapy with good clinical response

A 36-year-old Hispanic woman, covered with blisters since birth, was found to have markedly elevated chymotrypsin levels in her serum. This proteolytic enzyme is thought to digest laminin, thus causing separation of the basement membrane at the level of the lamina lucida, corroborating findings on electron microscopy. On the basis that the sun-exposed areas of the skin were relatively less involved, she received a course of UVB therapy, with total clinical clearance of her lesions after 3 weeks. A repeat estimation of serum chymotrypsin at this time revealed normal levels of this enzyme. It is thought that the elevated chymotrypsin levels were either released from the Langerhans cells themselves or from lymphocytes or keratinocytes as a result of Langerhans cell activity, and that the suppression of Langerhans cell activity by UVB inhibited the release of this proteolytic enzyme, resulting in the suppression of blister formation in our patient.

Pancreatic secretion by nonparallel exocytosis: potential resolution of a long controversy

The idea that pancreatic digestive enzyme secretion can occur in a nonparallel manner has been controversial because of its presumed incompatibility with the exocytosis secretory mechanism. Correlation and regression analysis of enzyme output by the rabbit pancreas after it is stimulated with cholecystokinin and chymodenin revealed that digestive enzymes are secreted in a highly linked fashion, compatible with exocytosis and with nonparallel secretion. Thus, exocytosis and nonparallel secretion are not contradictory processes, but rather nonparallel secretion is due to exocytosis from heterogeneous sources within the pancreas.

A novel proteinase from human pancreas

A cholesterol-binding protein was previously isolated from human pancreas [Sziegoleit (1982) Biochem. J. 207, 573-582] and shown to consist of a single polypeptide chain with an apparent Mr of 28 000 and an isoelectric point of pH 4.9. In further investigations, a proteolytic activity was observed to be present in preparations of this protein. The enzyme activity was not dissociable from the cholesterol-binding protein. It decreased in the presence of sodium dodecyl sulphate or urea parallel to degradation of the protein, indicating autodegradation in the presence of these denaturants. Glucagon digestion studies indicated the carbonyl bond of alanine to be a favoured site of the enzymic cleavage. The proteinase was inactive against chromogenic substrates relatively specific for elastase, trypsin and chymotrypsin, but was found to cleave benzyloxycarbonylalanine p-nitrophenyl ester efficiently. The enzyme was inactivated by phenylmethanesulphonyl fluoride and was thus classified as a serine proteinase. Autoradiographic studies demonstrated binding to serum alpha 1-antitrypsin and alpha 2-macroglobulin in a similar manner to that observed with other pancreatic endo-proteinases. The collective results indicate that the isolated protein, provisionally named 'cholesterol-binding pancreatic proteinase', is a novel proteinase of the human pancreas. Quantitative measurements indicate that it comprises 4-6% of total protein in pancreatic secretions.

Purification and characterization of proteases from the polychaete annelid Sabellaria alveolata (L.)

Eleven proteases have been purified to electrophoretic homogeneity from crude digestive fluid of polychaete annelids, Sabellaria alveolata. Purification steps were Sephadex G-100 gel filtration, benzamidine-cellulose and SBTI-Sepharose (SBTI = soybean trypsin inhibitor) affinity chromatography, CM-Sepharose and DEAE-Sepharose ion-exchange chromatography. Nine proteases have been purified in sufficient quantities for characterization. All are active at basic pH and are probably serine proteases, since they are inhibited by phenylmethylsulfonyl fluoride, specific chloromethyl ketone amino acids derivatives, but not by EDTA and p-chloromercuribenzoate. They do not hydrolyse exopeptidase substrates. From their properties, they can be divided into five classes. 1. A trypsin-like protease, which hydrolyses only trypsin substrates and is inhibited by N-tosyl-L-lysine chloromethyl ketone (TosLysCH2Cl), leupeptin and antipain. It differs from bovine trypsin by its very acidic isoelectric point (below 3.3) and its higher Mr (35 000). 2. A chymotrypsin-like protease which hydrolyses only chymotrypsin substrates and is inhibited by TosPheCH2Cl, Z-PheCH2Cl, chymostatin but only slightly by leupeptin and antipain. Its isoelectric point is below 3.3 and its Mr 31 000. 3. Two minor chymotrypsin-like proteases with slightly broader specificity, since they hydrolyse trypsin substrates significantly and are much more inhibited by leupeptin. They have acidic isoelectric points (3.3 and 3.5) and slightly lower Mr (27 000). 4. Four proteases hydrolyse trypsin and chymotrypsin substrates equally well. Their chymotryptic character is, however, predominant since they are inhibited by TosPheCH2Cl and Z-PheCH2Cl but not TosLysCH2Cl. They have similar Mr (27 000) but isoelectric points ranging from 4.0 to above 9.1. 5. The last one is very similar but has lower esterolytic activities. These proteases of broad specificity do not resemble any known serine protease since they differ from subtilisins by their sensitivity to TosPheCH2Cl.

Production of acute hemorrhagic pancreatitis in the dog using venom of the scorpion, Buthus quinquestriatus

Acute hemorrhagic pancreatitis has been produced in dogs by two separate intraarterial injections (20 and 10 micrograms/kg) of venom from the scorpion Buthus quinquestriatus. Morphological changes related to the development of the disease were detectable by electron and light microscopy at 1 and 3 hr, respectively, following the injection of venom. Six hours following venom injection, widespread areas of hemorrhage and fat necrosis were observed on the surface of the pancreas and adjacent mesenteries. By 24 hr, areas of fat necrosis more than 1 cm in diameter were present on the surface of the pancreas. No free protease was found in pure pancreatic juice collected at 3, 6, 24, and 96 hr after the injection of Buthus quinquestriatus venom. Amylase concentrations in serum increased to a maximum sevenfold above the basal level at 6-8 hr after injection. Since acute hemorrhagic pancreatitis occurred both with and without pancreatic duct cannulation, it is likely that the pathological process is independent of any venom effect on papillary sphincter tone. The morphological characteristics of the experimental disease appear similar to those observed at autopsy in acute hemorrhagic pancreatitis in humans.

Abnormalities in pancreatic secretory profiles of patients with cancer of the pancreas

Pancreatic secretory profiles for 11 pancreatic enzymes and proteins were established in nine patients with cancer of the pancreas by analysis of minute-to-minute collections of pure pancreatic juice after sequential administration of secretin and cholecystokinin. Aspiration of pancreatic fluid sufficient for this study was successful in less than one quarter of the patients investigated because of ductal obstruction and/or the effect of the disease on pancreatic exocrine function. Flow rates in patients generally were lower than in healthy individuals, and secretion of total protein, trypsin inhibitor, and activity of digestive enzymes were in the lowest part of or below the normal range. Normal flow rates in four patients precluded ductal obstruction as the sole cause of impaired enzyme secretion. Activity of lysosomal hydrolases in pancreatic juice of these patients, in contrast to that of digestive enzymes, remained within or rose above the normal range. The tumor appeared to have a diametrically opposite effect on the two different groups of enzymes. This is illustrated most dramatically in the form of ratios of lysosomal to digestive enzymes. Virtually all of 10 such ratios were far above the normal average in all patients, and none was below. In an analogous investigation of 25 patients with chronic pancreatitis only three exhibited the ratio pattern characteristic of pancreatic cancer patients. Pancreatic secretory profiles appear to be capable of discriminating between cancer of the pancreas and chronic pancreatitis in a high percentage of cases. Extension and refinement of this approach may facilitate early detection of cancer of the pancreas.

Effects of scorpion and rattlesnake venoms on the canine pancreas following pancreaticoduodenal arterial injections

Three scorpion venoms caused a transitory decrease in the rate of fluid secretion and increases in the concentration, in pancreatic juice, of total protein and individual enzymes. Protein and enzyme elevations 4-7 fold over the basal levels were produced by the venom of Tityus bahiensis and 6-7 fold by venoms from Tityus serrulatus and Buthus quinquestriatus. Although these increases were smaller than those stimulated by the C-terminal octapeptide of cholecystokin (OP-CCK; 8-9 fold), the secretory responses were of longer duration, so that the total output of protein caused by each of the three venoms was significantly greater than that observed with OP-CCK. Although electron microscopy revealed evidence of widespread degeneration of acinar cells at 1 hr and more extensive damage at 2 hr following injection of scorpion venom, no free protease was detected in pancreatic secretion collected during this period. The scorpion venoms also caused hypersecretion of viscid saliva. In contrast, rattlesnake venom, had no detectable effect on salivation, pancreatic secretion or morphology of the pancreas.

Metabolic properties and ultrastructure of alveolar type II cells isolated with elastase

We used porcine pancreatic elastase to isolate type II cells from the lungs of rats; the yield and purity of the type II cells was better than that obtained by methods using trypsin. In 102 experiments we obtained 82 +/- 23 . 10(6) cells/rat, 68 +/- 11% (mean +/- S.D.) of which type II cells. This preparation of cells, when centrifuged over a discontinuous density gradient, yielded 25 +/- 10 . 10(6) cells/rat, 80 +/- 13% of which were type II cells (n = 102). The cells, after density gradient centrifugation, could be futher purified by centrifugal elutriation (94 +/- 3% type II cells, n = 22) or adherence in primary culture (94 +/- 2% type II cells, n = 34). Type II cells isolated with elastase are similar morphologically and biochemically to type II cells isolated from rats with trypsin. The preparations of cells appeared healthy by several different criteria: ultrastructure, exclusion of vital dye, lack of stimulation of oxygen consumption by exogenous sodium succinate, and linear rates of oxidation of [1-14C]palmitic acid and of incorporation of [1-14C]acetate into fatty acids. Type II cells consumed 75 +/- 20 nmol O2/10(6) cell per h, oxidized [1-14C]palmitic acid at a rate of 0.4 nmol/10(6) cells per h, and incorporated [1-14C]acetate into fatty acids at a rate of 7.5 nmol/10(6) cells per h.

alpha-Amylase of human pure pancreatic juice: effects of pancreatic disease and the occurrence of variant forms in pancreatic juice from healthy volunteers

Pure pancreatic juice (PPJ) from healthy human volunteers and from patients with pancreatic or liver disease was subjected to isoelectric focussing (IEF) and assayed for alpha-amylase activity. In PPJ from most normals, a single predominant form of amylase was found, comprising congruent to 83% of the total activity recovered, and having pIapp congruent to pH 6.8. In PPJ from six normals, variant principal forms of amylase were found at pH congruent to 6.4 or pH congruent to 7.3, in addition to the peak at pH 6.8. IEF patterns of PPJ from individuals with pancreatic or liver disease were indisquishable from patterns obtained with PPJ from the control group of healthy volunteers.

Trypsinogen variants in pancreatic juice of healthy volunteers, chronic alcoholics, and patients with pancreatitis and cancer of the pancreas

Polyacrylamide gel electrophoresis of pure pancreatic juice from 14 healthy normal subjects, 11 chronic alcoholics without detectable pancreatic disease, 15 patients with pancreatitis, and two with cancer of the pancreas consistently demonstrated the presence of two variants of trypsinogen with different electrophoretic mobilities. In healthy normal subjects the proportion of cationic to anionic trypsinogen was invariably greater than 1 and averaged about 2. In chronic alcoholics, patients with pancreatitis or cancer of the pancreas, this ratio, with a single exception, was below one and averaged about 0.45. The extraordinary consistency of these findings suggests that the quantitative relationship between cationic and anionic trypsinogen in human pancreatic juice may be a very sensitive indicator of incipient or existing pancreatic pathology. The most acceptable explanation for the reversal of the normal zymogen ratio in pancreatic disease is a selective increase in the synthesis of the anionic variant relative to that of the cationic species. Total trypsinogen concentrations differed widely from one another in the three patient groups, but the ratio of cationic to anionic trypsinogen exhibited little change and remained below 1. Our results also demonstrate for the first time a specific effect of chronic alcohol abuse on the secretory profile of a pancreatic enzyme in human subjects. A newly discovered minor, trypsinogen-like component of human pancreatic juice was found to be significantly increased in pancreatic juice of chronic alcoholics, decreased in pancreatic secretions of patients with pancreatitis, and barely detectable in those of two patients with cancer of the pancreas.

Enteropeptidase levels in duodenal juice of normal subjects and patients with gastrointestinal disease

Enteropeptidase, trypsin, and chymotrypsin activity in basal and secretin-stimulated duodenal juice of 20 normal adult volunteers and 15 patients with gastrotestinal disease were determined. All enzyme concentrations showed skew distributions, but fluctuations in the secretin-stimulated juices were less pronouced than in the basal secretions. Secretin administration had no influence on the release of enteropeptidase from human duodenal mucosa, but resulted in a very small increase in secretion of pancreatic enzymes. Six out of seven patients with chronic alcoholic pancreatitis or cancer of the pancreas exhibited highly significant elevations of enteropeptidase in their basal as well as secretin-stimulated duodenal juice. It is suggested that raised luminal enteropeptidase activity may be the result of pancreatic insufficiency or elevated blood glucagon concentrations.

In vitro stimulation of lymphocytes by neutral proteinases from human polymorphonuclear leukocyte granules

Two neutral proteinases from human polymorphonuclear leukocytes (PMN), an elastase and the chymotrypsin-like cathepsin G, were purified, and their actions on lymphocytes in culture were studied. Both PMN proteinases stimulate lymphocytes from human peripheral blood and from mouse spleen in vitro, but do not affect thymic cells from either normal or hydrocortisone-treated mice. In stimulated mouse spleen cell cultures, most of the developing blast cells bear surface immunoglobulins, and subsequently appear to engage in antibody synthesis. In their stimulatory action, the two PMN proteinases thus resemble the classic B-cell mitogen LPS and neutral pancreatic proteinases such as trypsin, chymotrypsin, and elastase. The effects of proteinase inhibitors indicate that lymphocyte stimulation is dependent on the proteolytic activity of the enzymes. This work suggests that PMN proteinases, which are released at sites of inflammation, may modulate the function of lymphocytes.