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U Behnke

Publications and source records attributed to U Behnke.

8 recordsLinked to original sources
PubMed1979

[Substrate specificity of a protease from Thermoactinomyces vulgaris].

The cleavage specificity of a protease from Thermoactinomyces vulgaris (thermitase) was determined by the insulin B-chain and the cleavability of casein and haemoglobin by this enzyme as compared to other proteases (trypsin, chymotrypsin, proteases from Bac. megaterium and cytophages). The most intense splitting effect on the substrates under investigation (insulin B-chain, casein and haemoglobin) is exerted by thermitase, i. e., the unspecificity of this enzyme is especially marked.

Caseins↗
PubMed1978

[Characterization of a protease from Thermoactinomyces vulgaris (thermitase). 3. Substrate specificity and properties of partially purified thermitase].

During the process of cultivation of Th. vulgaris several proteases are formed. In the present investigation the extensively purified major component was used. The substrate specificity was determined by means of 7 proteins, 7 amino acid esters, 5 fatty acid esters and 15 amino acid 4-nitroanilides. Among the protein substrates tested, urea denaturated hemoglobin was split best, followed by gelatin, casein, field bean protein, serum albumin and gluten. The weakest rate of hydrolysis was observed with elastin. In contrast to this acetyl-(L-ala)3-methylester, that is a substrate for elastase, was split best from all the esters tested. Only 8% of this activity could be found with the chymotrypsin substrates acetyl-L-tyr-ethylester and acetyl-L-phe-ethylester and 1% of the above activity with the trypsin substrates tosyl-L-arg-methylester and benzoyl-L-arg-methylester. The fatty acid esters and the p-nitroanilides were hydrolyzed much more slowly. The pH-optimum of thermitase was found in the weakly alkaline region of pH 7 to 9. There were only small differences between the individual high and low molecular substrates. The temperature optimum was between 60 and 75 degrees C for esters and p-nitroanilides as substrates and at 90 degrees C for casein. It should be mentioned that the enzyme was quickly inactivated at temperatures above 70 degrees C.

Hydrogen-Ion Concentration↗
PubMed1978

[Characterization of a protease from Thermoactinomyces vulgaris (thermitase). 1. Purification of thermitase].

The paper deals with the purification of the microbial protease preparation "thermitase" (submerged cultivation of Thermoactinomyces vulgaris; treatment of culture filtrate with ethanol or Na2SO4, vacuum drying of precipitate). The crude substance was purified by column chromatography on Sephadex G-75, DEAE-Cellulose and Sephadex G-50. The proteolytically active fractions were in each case united, freeze dried and tested for protein components and protease activity by gel electrophoresis. After passage of the third column the isolated protease (4.5 fold enrichment in the specific activity) was further characterized. The electropherogram (pH 8.9) presented a protease band moving to the anode which was accompanied by 2 very weak protease bands. Furthermore there could be detected a very active protease band (main component of Thermitase) as well as a side band with lower activity both moving to the cathode. The freeze dried preparation contained 85% protein and 4% carbohydrates (glucose as single monomer component after acid hydrolysis). A molecular weight of 11,000 was determined by chromatography on Sephadex G-75. This value is critically discussed. Hints are given for autolytic processes taking place during the purification procedure.

Micromonosporaceae↗
PubMed1978

[Characterization of a protease from Thermoactinomyces vulgaris (thermitase). 2. Single-step fine purification and protein-chemical characterization].

The fine purification of an alkaline protease (thermitase) from Thermoactinomyces vulgaris by means of isoelectrical focussing in the flat-bed procedure using granulated gel is reported. An Na2SO4-precipitated crude product serves as the starting material. Isoelectrical focussing leads in a single step to a highly purified protein with an uniform N-terminal end group. The enzyme has an IP at 9.0 and a mol. wt. of 37,400; it consists of a polypeptide chain with arginine as the N-terminal, and tyrosine as the C-terminal end group. In addition to an essential serine residue, a SH group could be demonstrated which is hardly accessible in the native enzyme. Furthermore, the influence of different protease inhibitors was studied.

Isoelectric Focusing↗
PubMed1975

[Formation of bitter peptides in cheese and from casein].

Whereas a slightly bitter taste is desirable in certain foods, it is an off-flavour in cheese which may even lead to unfitness for consumption. Bitter principles from cheese have been found to be peptides with molecular weights ranging from 2000 to 3000. For the purpose of further characterization, bitter peptides were isolated from enzymatic casein hydrolysates as well as from bitter cheese and purified. 30 proteases from different origins proved to be able to form peptides with bitter taste of varying intensity from casein. Present experience shows that the formation of bitter peptides during casein hydrolysis can be inhibited only to a very small measure. Bitter peptides are extrmely resistant to proteases, which is probably attributable to their high contents of hydrophobic amino acids and hydrophobic bonds. The detection of only N- or C-terminal amino acid in each of 11 different bitter peptides shows that peptide chains are present and not cyclic peptides as repeatedly assumed. It must be aimed at avoiding the cheese defect "bitter" by using appropriate starter cultures and rennet substitutes as little disposed as possible to produce bitter peptides.

Caseins↗