Detection and determination of lipase (acylglycerol hydrolase) activity from various sources

Methods for the detection and determination of lipases (acylglycerol hydrolases) and preparation of assays are reviewed including substrates, conditions and screening. Some newer methods for the determination of lipase activity are discussed. Several of these are: (a) titrimetry, (b) colorimetry of Cu soaps of free fatty acids (FFA), (c) colorimetry of chromophores in the acyl chain of FFA or in glycerol, (d) radioassay, (e) gas liquid chromatography, (f) enzymatic treatment of FFA and measurement of the resulting products, and (g) direct immunological determination of the lipase. Examples and sensitivities are given and advantages and disadvantages are described.

Effect of bombesin on serum immunoreactive trypsin in healthy subjects and in patients with chronic pancreatitis

We studied the effect of bombesin (9 ng/kg X min for 30 min by intravenous infusion) on serum immunoreactive trypsin in healthy subjects and in chronic pancreatitis patients. Bombesin administration caused a marked and significant increase of serum immunoreactive trypsin concentration in healthy subjects. The increase occurred in the first 15 min after the beginning of bombesin infusion and persisted for the duration of the study (2 h). In patients with chronic pancreatitis, the increase was much less pronounced. In these patients, the integrated immunoreactive trypsin response to bombesin was significantly correlated with bicarbonate, lipase, and chymotrypsin outputs into the duodenum. The response of serum immunoreactive trypsin to bombesin stimulation seems to vary according to the degree of pancreatic exocrine dysfunction and to reflect the functional capacity of acinar cell mass.

Metal-binding ligands in Viokase

The object of this study was to detect low molecular weight zinc binders in Viokase, a porcine pancreatic preparation used in the treatment of variant acrodermatitis enteropathica (AE). Extracts were centrifuged and ultrafiltered to yield a soluble fraction containing solutes of molecular weights less than or equal to 500 daltons. These were studied by modified gel chromatography (MGC) using sealed Sephadex G-15-120 columns equilibrated with buffered solvent systems containing either 5 ppm copper (II) or 5 ppm zinc (II). Eluted fractions were assayed for these metals by atomic absorption and for amino acids by various techniques. MGC profiles of ultrafiltrates resulted in a peak consisting of glutamic acid and another peak consisting of several amino acids. A third peak was due to metal ions. Citrate and picolinate have been claimed to be important zinc-binding ligands in Viokase, but neither was detectable by MGC, although small amounts of citrate or similar compounds were detected by the Furth and Herrmann reaction. Since amino acid ligands are easily detectable by MGC, and metal distribution among ligands is competitive in nature, the possibility of a role for citrate or picolinate as a zinc transporter in Viokase is seriously reduced. Relief to the variant AE patient was probably not due to citrate- or picolinate-enhanced zinc uptake.

Further characterization of the bile salt-stimulated lipase in human milk

Bile salt-stimulated lipase is a milk enzyme unique to the higher primates. Its molecular and kinetic characteristics differ greatly from other lipolytic enzymes; e.g., pancreatic lipase and lipoprotein lipase. It has a much higher app. Mr, 310000 on gel filtration and 100000 after denaturation. It requires primary bile salts for optimal activity and bile salts also protect the enzyme from proteolytic and heat inactivation. It may, due to its low substrate specificity, contribute to the utilization of a variety of milk lipids. Since it lacks positional specificity, digestion of milk triglycerides should be complete, which may explain why fat absorption is more efficient in breast-fed than in formula-fed infants.

Isolation and partial characterization of a complex of several (Pro-) endopeptidases from whole porcine pancreatic extract and from purified zymogen granules

Pancreatic zymogen granules contain exportable proteins at a very high concentration. The mechanism leading to this condensation is unknown. On the other hand, it is known that aqueous extract of pancreatic acetone powder precipitates at low ionic strength and acidic pH. The precipitable fraction is called 'euglobulin' in the literature. We thought that euglobulin could serve as a simplified model to study the condensation of some of the pancreatic exportable proteins. We have compared quantitatively and qualitatively the composition of euglobulins prepared from porcine pancreatic acetone powder and from lysates of purified pancreatic zymogen granules. They were found to be nearly identical, consisting of glycoprotein(s) and/or proteoglycan(s) associated to a proesterase activity, chymotrypsinogens C and D and proelastase. We conclude therefore, that the interactions between the constituents of euglobulin must be specific, since they can occur in the complex protein mixture of the whole organ to a similar extent as in the zymogen granules themselves. We have tried to identify the nature of these specific interactions. We were able to demonstrate that neither the granule membranes, nor the high-molecular-weight proteoglycan present in the granules (Reggio, H.A. and Palade, C.E. (1978) J. Cell. Biol. 77,288-314) were responsible for the observed aggregation. Electrostatic interactions between acidic and basic proteins (Thomson, A. and Denniss, I.S. (1976) Biochim. Biophys. Acta 429, 581-590) were demonstrated between proelastase and chymotrypsinogens C and D. However, the possible roles of the glycoprotein(s) and/or proteoglycan(s) in the condensation process remain unknown.

Growth, digestibility and enzymatic activities in the pancreas and intestines of hamsters fed raw and heated soy flour

The nutritional effects of feeding raw and heated soy flour to young golden Syrian hamsters were investigated over a period of 32 days. Those animals fed raw soy flour grew much more poorly than those fed heated soy flour, an effect which was reflected in a lower food efficiency as well. Growth retardation of hamsters fed raw soy flour was accompanied by a lower apparent digestibility of the protein (54%) compared to heated soy flour (76%). The pancreases of animals fed raw soy flour were increased in size and had elevated levels of trypsin, chymotrypsin, amylase, and lipase. With the exception of trypsin activity in the small intestine, similar differences in enzyme activities between the raw and heated soy groups were generally found in the small intestine, cecum, large intestine, and feces. There was, however, a progressive decrease in these activities in the lower regions of the intestinal tract and feces. It is concluded that the hamster, in common with several other species of animals, is sensitive to the effects of the trypsin inhibitors in raw soy flour, and may provide a useful model for studying the long-term effects of trypsin inhibitors on the pancreas.

Determination of alpha-amylase, trypsin and lipase in duodenal fluid: comparison of methods

The three most important enzymes present in duodenal fluid, alpha-amylase, trypsin and lipase, were determined by two different methods. Various dilution fluids for these determinations were compared. Some kinetic data are described together with the reproducibility of the assays. For alpha-amylase the Phadebas method was compared with an UV method. Trypsin was determined using an immunoreactive trypsin test and a titrimetric method, while lipase was determined with a titrimetric method and a Cu-soap method. There was very good agreement between the two alpha-amylase methods and between the two trypsin determinations. There was also good agreement between both lipase methods. The advantages and disadvantages of all the methods are discussed.

[The pathogenesis of otitis externa]

In otitis externa the formerly grampositive colonization of the auditory canal changes towards a gramnegative microbial flora. Pseudomonas aeruginosa plays a major role in recurrent infections and in swimmer's ears. Various serotypes of ps. aeruginosa i.e. type 1;6 and 5 could be isolated. In swimmer's ears ps. maltophilia was identified twice. There was no correlation between the severity of the disease and the protease and lipase activity of pseudomonas isolates. Exoenzyme activity seemed to bear influence on the chronicity of the disease. Therapeutic success led to a decline of enzymatic activity.

Effects of hydrocortisone and cholecystokinin-octapeptide on neonatal rat pancreas

Hydrocortisone and cholecystokinin-octapeptide (CCK-8) were injected into newborn rats on days 1-5 of life. Both agents induced significant increases in pancreatic weight, protein, DNA, and specific activities of amylase, chymotrypsinogen, and lipase. The ability of the pancreas to secrete amylase in response to carbachol was decreased by the administration of hydrocorticosterone at age 7 days. CCK-8 increased basal secretion at 7 days. We conclude that growth and secretory capacity of the newborn rat pancreas are under the control of both glucocorticoids and cholecystokinin.

[Determination of the catalytic activity of lipase by the continuous titration method]

Development of a standardized procedure for the titrimetric assay of lipase has been suggested. Comparative studies with triolein und olive oil were therefore undertaken. Optimal conditions, such as pH, substrate and glycocholate concentrations, etc. were determined for the assay with triolein. The results agree with those obtained earlier with olive oil as substrate. Experience with the quality of various reagents used since 1966 is reported. Problems of methodology are then discussed, especially the incomplete characterization and purity of the bile acid preparations, and their effects on the test conditions. A critical analysis shows that two point tests with modifications of the continuous titration cannot give reliable results. Haemolysis and its effect on catalytic activity of lipase are used to illustrate the consequences of the uncritical acceptance of data from the literature. Furthermore, the required sensitivity of the analytical equipment, operational errors, and the uncritical evaluation and interpretation of analytical data are discussed. The first experiments to be performed with the addition of colipase are described, and the question of whether this cofactor should be used routinely for test purposes is considered. The problem of whether lipoproteinlipase can be quantitatively inhibited is discussed. In view of the outlay on apparatus and the time required for the assay, continuous titration is definitely not suitable for routine screening purposes. On the other hand, simpler methods that give reproducible quantitative results have not yet been developed.

Modulation by phenobarbital of lipolytic activity in postheparin plasma and tissues of the rat

Male rats injected with phenobarbital at a dose of 100 mg/kg for 5 days manifested increased postheparin lipolytic activity of fasting plasma. Inhibition studies with protamine sulphate, 1 M NaCl, and sodium dodecyl sulphate revealed that the activities of both lipoprotein lipase and hepatic triacylglycerol lipase were increased in the postheparin plasma of the drug-treated rats. Adipose tissue lipoprotein lipase activity was also increased in the phenobarbital-treated rats. The triacylglycerol lipase activity elutable by heparin from liver slices and the residual activity of liver microsomes increased significantly in the drug-treated rats. Lipoprotein lipase of cardiac muscle and red skeletal muscle was unaltered by phenobarbital treatment. The increased postheparin lipolytic activity of fasting phenobarbital-treated rats seems to be accountable through increased lipoprotein lipase activity of adipose tissue and increased triacylglycerol lipase activity of liver, both of which may contribute to the lowered fasting concentrations of serum triacylglycerol mediated by the drug, as previously reported.

[Determination of the catalytic activity of lipase with trilinolein as substrate]

The applicability of the two point test reported by Proelss & Wright ((1977) Clin. Chem. 23, 522-531) for the determination of lipase was investigated. The substrate, trilinolein, is indeed cleaved by pancreatic lipase without interference from liver esterase or cholinesterase; on the other hand, the reported colour reaction gives nonreproducible results. Furthermore, the continuous UV-test showed a lag phase, the duration of which depends on the added catalytic activity. For these reasons the method of Proelss & Wright for the determination of lipase in serum does not give diagnostically useful results.

Phagocytosis in leprosy. 5. The effect of the infection with Mycobacterium lepraemurium on the level of diverse hydrolytic lysosomal enzymes of murine peritoneal macrophages

The effect of the infection with M. lepraemurium on the activity of several lysosomal enzymes of mouse peritoneal cells was studied. The enzymes studies were acid- and alkaline-phosphatases, acid (cathepsin D-type) proteinase, beta-glucuronidase, deoxyribonuclease, a nonspecific lipase, and lysozyme. Enzyme determinations were carried out four months and six months after the infection with 15.5 X 10(7) bacilli per mouse. Clear differences between M. lepraemurium-infected and normal animals were observed at four months of infection, with all of the mentioned enzyme activities well above the normal values. At six months of infection, a tendency to decrease to normal values of the enzyme activities was observed. It is suggested that this biochemical activation of mouse peritoneal cells reflects the effect of the cell-mediated immune response triggered by the infection with the murine leprosy bacillus. M. lepraemurium-infected mice possess macrophages in a high state of biochemical activation; yet, they are unable to get rid of the infecting microorganism.

Studies on salivary and pancreatic lipases of the pre-ruminant calf

Salivary and pancreatic lipases of the pre-ruminant calf have been studied using ion-exchange chromatography and gel filtration. In addition, pancreatic lipase has been fractionated using concanavalin A-affinity chromatography. The effects of 5,5'-dithiobis(2-nitrobenzoic acid), organic solvents and trypsin on pancreatic lipase have also been investigated. The effects of taurodeoxycholate on the lipolytic activity of the 2 lipases has been compared. Salivary lipase behaved as a single enzyme on ion-exchange chromatography, and gel filtration gave a mol. wt value of 52,000 for the enzyme. Although pancreatic lipase appeared to be a single enzyme on gel filtration, with a mol. wt of almost 80,000, the lipase was shown by ion-exchange and affinity chromatography to consist of at least 2 enzymes of mol. wts 72,000 and 60,000, and did not require colipase for maximum activity in the presence of high concentrations of bile salts. Colipase-dependent lipase, mol. wt about 45,000, and probably amounting to not more than 10% of the total activity, was also present. This was the predominant form only after large losses in total lipolytic activity had occurred, as after treatment with a mixture of ether, ethanol and deoxycholate, or prolonged action of trypsin. When the concentration of taurodeoxycholate was increased from zero to 1 mM in a tributyrin substrate, the lipolytic activities of calf salivary and pancreatic lipases, and pig pancreatic lipase, increased. At a concentration of 4 mM-taurodeoxycholate, calf salivary lipase activity was higher, that of calf pancreatic lipase lower and pig pancreatic lipase activity markedly lower.

Exoenzymes of Propionibacterium acnes

Thirty strains of Propionibacterium acnes were grown in basal salt medium containing lecithin as a lipid substrate and in other media. The cultures were assayed for production of lipase (measured as fatty acid esterase) and other exoenzymes. Lipase was assayed spectrophotometrically; other enzymes were assayed using the API ZYM system (Analytab Products Inc., Plainview, NY). Substance for lipase were alpha- and beta-naphthol esters of propionic, butyric, valeric, caprylic, lauric, myristic, and oleic acids. All strains showed fatty acid esterase activity. Using the API ZYM system 19 enzymes were detected, 8 of which were found frequently and had high activity in most strains. Acid and alkaline phosphatases, phosphoamidase, ester lipase, trypsin-chymotrypsin-like proteases, beta-glucuronidase (80%), beta-galactosidase (80%), and N-acetyl-beta-glucosaminidase were found. Many enzymes of P. acnes appear to be adaptive, dependent on the culture substrate.

Alterations of exocrine pancreatic enzymes in virus-induced diabetic cattle as revealed by immunohistochemistry

The pancreatic tissue of normal and virus-induced diabetic cattle was investigated by the indirect immunofluorescence technique. Seven secretory proteins (chymotrypsinogen A, trypsinogen, carboxypeptidase A, RNase, DNase, alpha-amylase and lipase) were localized in normal bovine pancreatic acinar cells but in diabetic animals amylase, lipase and carboxypeptidase were either not detectable or markedly diminished. Decrease in amylase content has been reported previously in other diabetic animals. The diminution of the three pancreatic enzymes may be related to the destruction of pancreatic endocrine tissue that occurs in these diabetic animals.