Assay of trypsin activity of human serum with a chromogenic substrate, CBZ-diglycyl-l-arginyl-2-naphthylamide hydrochloride (GGANA)

Adaptive response of the rat pancreas to dietary substrates: parallel regulation of trypsinogen and pancreatic secretory trypsin inhibitor

Chronic pancreatitis has been associated with malnutrition in alcoholic patients and malnourished juveniles. The composition of the diet, especially the protein content, regulates the synthesis of secretory proteins in the rat pancreas. Adaptive responses of the pancreas have shown that anionic proteases (e.g., trypsinogen) are upregulated during protein deprivation. We hypothesize that the (cationic) pancreatic secretory trypsin inhibitor (PSTI) is down-regulated after a protein-deficient diet. Low PSTI levels might cause a lack of protection from prematurely activated trypsin and therefore enhance the risk for pancreatic inflammation. Over a period of 1 month, rats were fed one of four isocaloric diets with a casein content varying from 0 to 82%. PSTI and trypsinogen mRNA remained fairly constant, irrespective of the diet composition. Trypsinogen and elastase secreted into pancreatic juice were upregulated after a protein-deficient diet relative to a control diet. Contrary to our hypothesis, PSTI was also upregulated. Parallel secretion of trypsinogen and PSTI appears to ensure protection against premature activation even under extreme dietary conditions.

An extracellular proteasome-like structure from C6 astrocytoma cells with serine collagenase IV activity and metallo-dependent activity on alpha-casein and beta-insulin

An extracellular proteasome-like (EP) structure has been isolated from serum-free media conditioned by C6 astrocytoma cells. EP has a native molecular mass of 1000 kDa and is composed of three subunits, two isoelectric variants at 70 kDa and one at 65 kDa. The extracellular proteasome degraded collagen IV, alpha-casein, beta-insulin, and certain synthetic peptide substrates. A 68-kDa type IV collagenase, identified as the activated form of gelatinase A, was also isolated from this medium. The type IV collagenase activity of the proteasome was sensitive to serine protease inhibitors, while the 68-kDa collagenase IV represented the matrix metalloprotease gelatinase A. The general protease activity of the proteasome was sensitive to metalloprotease inhibitors. Western blot analysis indicates a sequence relationship between the 68-kDa type IV collagenase and either one or both of the 70-kDa isoelectric variants of the proteasome; however, the two enzymes appear to be distinct functionally. Comparison with known proteasomes indicates that EP represents a novel proteasome. The complexity of degradative enzymes in the extracellular microenvironment implies that complete inhibition of tumor growth requires at least a combination of serine and metalloprotease inhibitors.

Correlation of trypsin-plasma inhibitor complexes with mortality in experimental pancreatitis in rats

Activation of trypsinogen in acute pancreatitis results in subsequent increases in plasma levels of trypsin bound to the inhibitors alpha 1-protease inhibitor (alpha 1-PI) and alpha-macroglobulin (alpha-M). It seems logical to speculate that plasma levels of these inhibitor-bound forms of trypsin may reflect the degree of intrapancreatic zymogen activation and that determination of such parameters may be of diagnostic and prognostic value. In order to test this hypothesis, the concentrations of trypsinogen and of trypsin bound to alpha 1-PI have been determined in serial plasma samples from rats who died (N = 7) and survived (N = 5) following induction of pancreatitis with taurocholate. Since the other major reaction product of active trypsin in plasma, alpha-macroglobulin-bound trypsin, cannot be measured directly, the plasma levels of trypsin-like amidase activity were determined to estimate the concentration of trypsin-alpha-M complex. Shortly after induction of pancreatitis, elevated levels of trypsinogen were present in plasma, but no alpha 1-PI-bound trypsin could be detected. Trypsin-alpha 1-PI complex continuously increased over the time course of pancreatitis in animals that died. In contrast, the plasma levels of trypsin-alpha 1-PI complex were lower in animals that survived, peaked around 15 hr postinduction at levels (182 +/- 53 ng/ml) significantly lower than those in dying animals (543 +/- 346 ng/ml), and fell during the following 48 hr. There was a significant correlation between plasma trypsin-like amidase activity and plasma alpha 1-PI-bound trypsin. Our data demonstrate that the concentration of activated forms of plasma trypsin in the bloodstream are correlated with mortality in experimental pancreatitis.

Fluorometric microassay of trypsin and enteropeptidase in children--comparison with a titrimetic assay

Two trypsin assay methods for the estimation of this enzyme in duodenal fluid from children have been compared. Assay results for a fluorometric method based on the use of N-carbobenzoxy-diglycyl-L-arginyl-2-naphthylamide hydrochloride (GANA) as the trypsin substrate were found to correlate well (r = 0.91, P less than 0.001) with those obtained with a much less sensitive titrimetric assay which used benzoylarginine ethylester hydrochloride (BAEE) as substrate. The higher sensitivity of the fluorometric assay has allowed accurate determination of trypsin activity in 10 microliter aliquots of duodenal fluid. This low volume requirement makes the assay suitable for studies on infants of all ages and conserves duodenal fluid for use in other investigations often warranted during the assessment of childhood malabsorption. The fluorometric assay has also been used to monitor the separation of enteropeptidase from trypsin(ogen) by chromatography on Sephacryl S-200 in samples of duodenal fluid from two children. Different proteolytic pathway deficiencies were confirmed in these children.

A new, highly sensitive and specific assay for chymotrypsin

1. A simple, highly sensitive, specific fluorometric method for the determination of chymotrypsin is described. 2. The new substrate utilized in this assay, N-glutaryl-glycyl-glycyl-l-phenylalanine beta-naphthylamide (GGPNA), is readily soluble in water, stable and highly specific for chymotrypsin. It is not degraded by a large excess of carboxypeptidase B, elastase, thrombin or plasmin and is virtually resistant to trypsin. 3. GGPNA is extremely sensitive to the action of chymotrypsin and permits detection of enzyme concentrations as low as 1 ng/ml. Linearity between enzyme concentration and fluorescence produced is maintained up to at least 3000 ng/ml. 4. alpha2-Macroglobulin-bound chymotrypsin hydrolyzes GGPNA at a rate about 2/3 of that exhibited by the free enzyme. 5. Bile pigments in amounts normally found in duodenal juice or traces of blood do not interfere with the assay. 6. GG PNA which releases beta-naphthylamine upon hydrolysis is suitable also for colorimetric and histological determination of chymotrypsin.