Xylanolytic activity of commercial juice-processing enzyme preparations

Of 22 commercial juice-processing enzyme preparations investigated, Clarex ML was found to exhibit the highest xylanase activity. The xylanase from Clarex ML was most active at 50–60°C and pH 5·0–5·5. The K _m and V _max values of the enzyme with oat-spelt xylan as the substrate were 8·6 mg ml⁻¹ and 42 μmol xylose l⁻¹ min⁻¹, respectively. Xylobiose was the main product of enzymatic hydrolysis of xylan.     

Glucosyltransferase activity of commercial juice-processing enzyme preparations

Of various commercial enzyme preparations examined, Cytolase M102 was found to contain the highest glucosyltransferase activity (55 U ml⁻¹). It rapidly converted maltose to panose (Glcα1 → 6Glcα1 → 4Glc) with a V _max value of 5·8 mmol l⁻¹ min⁻¹ at 50°C in 0·05 mol l⁻¹ sodium acetate buffer (pH 4·4). The K _m value of the enzyme for maltose was 750 mmol l⁻¹. Yields of panose and glucose after 45 min of reaction, for example, were 47·2% and 52·8%, respectively, on the basis of the amount of maltose consumed.     

Cellulase activity in commercial lipase preparations

Polymeric membranes are increasingly used as supports for the immobilization of enzymes in bioreactors. One of the more common reactor types employed in lipase-catalyzed hydrolysis of oils, contains modified cellulose as a membrane material. We found that this type of material is readily attacked by cellulase present in several commercially available lipase preparations. This leads to membrane damage, reactor instability, and leakage. We conclude that cellulose membranes are not suitable as supports in bioreactors for the immobilizartion of these lipases. The development of alternative membranes is currently in progress. (c) 1992 John Wiley & Sons, Inc.     

Antiviral activity of commercial immunoglobulin preparations

Immunoglobulin preparations for intravenous use of five different firms--Biotest, Hoechst, Merieux, Sandoz, WWSS--were used for the study. Antibody level for Epstein-Barr, cytomegalia, herpes simplex, varicella-zoster and measles viruses was determined in these preparations stored at 4 degrees C and in order to determine their stability they were tested after incubation at 37 degrees C and 61 degrees C. The influence of immunoglobulin (Bioglobulin and Sandoglobulin) on mouse survival infected with HSV-1 was determined. Results of serological studies revealed differentiated antibody level for particular virus antigens both in various series of a given preparation as well as between immunoglobulins of different producers. Protective activity of immunoglobulin was mainly found when given 24 hours before challenge with HSV-1. This was the case not only when preparations stored at 4 degrees C were given but also for those which were incubated at 37 degrees C for months. Forty percent higher rate of survival of mice as compared to control group was seen when immunoglobulin were given 8 hours after infection.     

Studies on proteolytic activity in commercial myoglobin preparations

Commercial myoglobin preparations from horse skeletal muscle degraded casein. The maximum activity was at pH8-8.5. A muscle myofibril preparation was also attacked. The protease could be partly separated from the myoglobin by selective ultrafiltration through a membrane with an exclusion limit of mol.wt. 30000. A greater than 1000-fold purification of the proteolytic activity was achieved by affinity chromatography with soya-bean trypsin inhibitor bound to CM-cellulose. The enzyme preparation hydrolysed p-toluenesulphonyl-l-arginine methyl ester and N-benzyloxycarbonyl-l-tyrosine p-nitrophenyl ester. Its activity was inhibited strongly by soya-bean and ovomucoid trypsin inhibitors, serum and the soluble fraction of muscle homogenates. EDTA, p-chloromercuribenzoate and phenylmethylsulphonyl fluoride also caused some inhibition.     

Amine oxidase activity in commercial preparations of bovine serum albumin

Amine oxidase activity has been identified in commercial samples of bovine serum albumin (BSA). Benzylamine, phenylethylamines and to a lesser extent, indoleamines, were found to be substrates. The amine oxidase activity was inhibited by semicarbazide and was virtually absent in electrophoretically purified samples. Kinetic analysis of benzylamine deamination and experiments utilizing mixed substrates indicate that more than one catalytic activity may be involved. The results show that amine deamination should be considered as a potential source of error in experiments employing high concentrations of commercially available BSA preparations. This would be of particular importance for $\text{in vitro}$ studies with dopamine since this amine was found to be deaminated at a rapid rate.     

Comparison of the hydrolytic activity of commercial cellulase preparations

Summary Two different quality types of sugar-cane molasses containing a total sugar content of 48%–50% (w/v) and 35%–42% (w/v) were investigated for Zymomonas biothanol production. Molasses concentrations of up to 250 g/l (1:3 dilution) were successfully fermented within 24 h despite a higher salt concentration in the lower grade molasses. Higher molasses concentrations (300 g/l) led to fructose accumulation. The addition of sucrose to a final sugar concentration of 15% (w/v) led to 10% (v/v) ethanol with conversion efficiencies up to 96%. Sorbitol levels were negligible, but increased up to tenfold upon addition of invertase. Offprint requests to: H. W. Doelle     

On the presence of proteolytic activity in glycosaminoglycan-degrading enzyme preparations

A solid-phase protease assay has been used to screen different commercial preparations of glycosaminoglycan-degrading enzymes for the presence of proteolytic activity. Proteases cannot be detected in preparations of testicular hyaluronidase and of chondroitinase at the concentration used for histochemical purposes. Commercial Streptomyces hyaluronidase contains proteolytic contaminants detectable at the concentration used for histochemistry. At higher concentrations, all preparations appear to be contaminated with proteases. The results obtained using this assay suggest that addition of a mixture of proteinase inhibitors containing N-ethylmaleimide, EDTA, pepstatin, and phenylmethanesulfonylfluoride or soybean trypsin inhibitor has little effect on the proteolytic activity of the glycosaminoglycan-degrading enzyme preparations, irrespective of the pH used. Moreover, the use of EDTA in this mixture is questionable. This study also describes two testicular hyaluronidase preparations that may be particularly useful in functional studies of the living organism, as they are only slightly contaminated.     

Identification of the trypsin-like activity in commercial preparations of eel acetylcholinesterase.

Electricus electrophorus acetylcholinesterase (AChE, EC 3.1.1.7) is reported to possess a trypsin-like activity. We found that purification of AChE removes over 99% of this protease activity, which resides in a single 25 kDa protein with an N-terminal sequence identical to bovine pancreatic trypsin. Digests of neuropeptides using purified eel AChE or bovine pancreatic trypsin gave identical peptide maps. These results indicate that the commercial preparation of eel AChE is contaminated by a trypsin, which is difficult to remove completely during AChE purification.     

Admixture in commercial tetracycline preparations

The content of admixtures in tetracycline stored under different conditions was determined with chromatographic and spectrophotometric methods. Biological activity, toxicity and colour of the drugs was tested. The changes in teh colour of tetracycline most pronounced on its storage at a temperature of 37 degrees C and elevated humidity were not accompanied by an increase in the content of anhydrotetracyclines. In parallel with the changes in the colour of tetracycline, the loss of its biological activity up to 30 per cent and increased toxicity were registered. The LD50 decreased by 40 per cent as compared to the initial level. Simultaneously an additional spot with high chromatographic mobility (Rf 0.98--1.0) was detected on thin-layer chromatograms. It was shown that the processes of tetracycline degradation resulting in marked darkening of the drug colour were not accompanied by an increase in the content of anhydro admixtures. They were probably the result of accumulation of other products which are as highly toxic and low active as the anhydroderivatives of tetracycline.     

Fructosyltransferase activity of a glucan-binding protein from Streptococcus mutans

Streptococcus mutans serotype c produces several extracellular proteins which bind to affinity columns of immobilized glucans. The proteins are three distinct glucosyltransferases and another glucan-binding protein (molecular weight 74000) which is now shown to be a fructosyltransferase. This enzyme is antigenically distinct and genetically independent of two other fructosyltransferases produced by the same organism. A mutant is described which lacks the glucan binding fructosyltransferase and has defective ability to form adherent colonies in the presence of sucrose. Although the production of glucans from sucrose results in the glucan binding protein becoming bound to the bacterial surface, and hence perhaps contributing to adherence, the fructans synthesized by the enzyme do not appear to contribute to this phenomenon.     

Arylsulfatase inactivation of slow reacting substance. Evidence for proteolysis as a major mechanism when ordinary commercial preparations of the enzyme are used

Type II B arylsulfatases are known to inactivate slow reacting substance (SRS), but the mechanism is unclear. In the present study, ordinary commercial preparations of Sigma limpet arylsulfatase largely inactivated the glutathionyl and cysteinyl-glycyl forms of SRS, but the cysteinyl form of SRS was largely resistant to the enzyme. Evidence is presented which established that a major mechanism for the inactivation of the glutathionyl and cysteinyl-glycyl SRS types, at least by the particular enzyme preparations we have studied, involves cleavage of the glycine moiety from the sulfur containing side chain. This was confirmed by digestion studies with glutathione itself. In addition, there is ome evidence to indicate that the enzyme may destabilize the double bond structure of the SRS molecule, contributing to the overall inactivation.     

Comparison of hydrolytic activity in water and heptane for thirty-two commercial lipase preparations

The protein content and the rates of hydrolysis of p-nitrophenyl palmitate (pNPP) in water (soluble enzyme and emulsified substrate) and in heptane (soluble substrate and insoluble enzyme) were measured for thirty-two commercial lipase preparations. The protein content of the powders varied in a wide range as well as the activity on emulsified pNPP showing the high heterogeneity of the commercial samples. Activity in heptane also varied but to a lesser extent than that in water. There was no direct correlation between activities in water and in heptane as assayed with the same hydrolytic reaction. The ratio of activity in heptane to that in water, R(O/A) ratio, was introduced to characterize activity in organic media. Six lipases showed R(O/A) values higher than 1 demonstrating a higher activity in organic solvent than in water. A linear correlation of R(O/A) with activity in water (log plot) suggested the strong influence of diffusional limitations on activity of solid enzyme suspended in organic solvents.     

Aryl sulfatase inactivation of slow reacting substance. Evidence for proteolysis as a major mechanism when ordinary commercial preparations of the enzyme are used

Type II B arylsulfatases are known to inactivate slow reacting substance (SRS), but the mechanism is unclear. In the present study, ordinary commercial preparations of Sigma limpet arylsulfatase largely inactivated the glutathionyl and cysteinyl-glycyl forms of SRS, but the cysteinyl form of SRS was largely resistant to the enzyme. Evidence is presented which established that a major mechanism for the inactivation of the glutathionyl and cysteinyl-glycyl SRS types, at least by the particular enzyme preparations we have studied, involves cleavage of the glycine moiety from the sulfur containing side chain. This was confirmed by digestion studies with glutathione itself. In addition, there is some evidence to indicate that the enzyme may destabilize the double bond structure of the SRS molecule, contributing to the overall inactivation.     

Clarification of fruit juice with chitosan

Chitosan prepared from shrimp shell was made partially water-soluble by hydrolyzing with 7% acetic acid. This chitosan at low concentration was found to be effective in the clarification of different fruit juices. Appearance and acceptability of the juices after treatment with chitosan significantly increased on a nine point Hedonic scale.