Authors:G. D'Andrea, V. Mucciante, and F. Fantauzzi
At 298.15 K, the solubilization of hen ovotransferrin at buffered pH 7.8 (0.08 M Tris⋅HCl buffer, containing 0.1 M CaCl2) and the solubilization of α-chymotrypsin (from bovine pancreas) at non-buffered pH 3.0 (0.001 M HCl) both resulted in large
exothermic reactions, being the apparent ΔHs –2485 in the first case and –780.1 kJ mol–1 in the second case, respectively. By contrast, the complete hydrolysis of ovotransferrin (pH 7.8) achieved by using a-chymotrypsin
(pH 3.0) gave an endothermic reaction with ΔH=+31.84 kJ mol–1.
Authors:L. Kredics, Zsuzsanna Antal, A. Szekeres, L. Manczinger, Ilona Dóczi, F. Kevei, and Elisabeth Nagy
Species belonging to the filamentous fungal genus Trichoderma are well known as potential candidates for the biological control of plant pathogenic fungi and as cellulase producers of biotechnological importance. Several data were published in the last decade also about the clinical importance of this genus, indicating that Trichoderma strains may be potential opportunistic pathogens in immunocompromised patients. However, there is a lack of information about the potential virulence factors of clinical Trichoderma strains. This study was designed to examine the extracellular proteolytic enzymes of six clinical T. longibrachiatum isolates. Supernatants from induced liquid cultures of the examined strains were screened for proteolytic enzyme activities with 11 different chromogenic p-nitroaniline substrates. The production of trypsin-like, chymotrypsin-like and chymoelastase-like protease activities cleaving N-Benzoyl-L-Phe-L-Val-L-Arg-p-nitroanilide, N-Succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide,and N-Succinyl-L- Ala-L-Ala-L-Pro-L-Leu-p-nitroanilide, respectively, was common among the strains examined. Separation of trypsin- and chymotrypsin-like activities by column chromatography revealed, that both systems are complex consisting of several isoenzymes. The pH-dependence of these two protease systems was also studied. Based on the results, the different isoenzymes seem to have different optimal pH values. Extracellular proteolytic enzymes may be involved in the pathogenecity of Trichoderma strains as facultative human pathogens.
Authors:R. Kumar, V. Choudhary, S. Mishra, and I. Varma
Optimum temperature and pH for the isolation of soy protein isolate (SPI) from soy protein concentrate (SPC) were established.
Enzymatic hydrolysis of SPI with enzymes of different specificities such as trypsin, chymotrypsin, papain and urease was carried
out and the products of hydrolysis were characterized by molecular mass determination [sodium dodecyl sulfate-polyacrylamide
gel electrophoresis (SDS-PAGE)] and thermal techniques [differential scanning calorimetry (DSC) and thermogravimetric analysis
(TG)]. Enzymatic hydrolysis resulted in a significant reduction in molecular masses. However the thermal stability of hydrolysed
SPI was similar to native SPI indicating that it is independent of molecular mass. DSC studies indicated an increase in temperatures
of endothermic transition associated with SPI denaturation and loss of absorbed moisture in samples of lower molecular masses.
Authors:L. Kredics, Zsuzsanna Antal, A. Szekeres, L. Hatvani, L. Manczinger, Cs. Vágvölgyi, and Erzsébet Nagy
Cellulolytic, xylanolytic, chitinolytic and b-1,3-glucanolytic enzyme systems of species belonging to the filamentous fungal genus Trichoderma have been investigated in details and are well characterised. The ability of Trichoderma strains to produce extracellular proteases has also been known for a long time, however, the proteolytic enzyme system is relatively unknown in this genus. Fortunately, in the recent years more and more attention is focused on the research in this field. The role of Trichoderma proteases in the biological control of plant pathogenic fungi and nematodes has been demonstrated, and it is also suspected that they may be important for the competitive saprophytic ability of green mould isolates and may represent potential virulence factors of Trichoderma strains as emerging fungal pathogens of clinical importance. The aim of this review is to summarize the information available about the extracellular proteases of Trichoderma. Numerous studies are available about the extracellular proteolytic enzyme profiles of Trichoderma strains and about the effect of abiotic environmental factors on protease activities. A number of protease enzymes have been purified to homogeneity and some protease encoding genes have been cloned and characterized. These results will be reviewed and the role of Trichoderma proteases in biological control as well as their advantages and disadvantages in biotechnology will be discussed.
The paper investigates the effect of glutathione on model biological systems, such as enzymes, (lisozyme, alcoholdehydrogenase,
α-chymotrypsin) and DNA base components. Our results on the inactivation of enzymes and on the chemical changes in DNA base
components show a radioprotective action of glutathione in all systems. The results are discussed in terms of glutathione
free radical reactivity and in the light of current hypothesis on the modification of the radiation damage given by thiol
Recent progress in thermodynamic aspects of proteins, free or immobilized on solid support, are described. In agreement with
results observed with Ribonuclease A , DSC analysis on α-chymotrypsin confirms a decoupling of melting domains with the
immobilized protein in a large range ofpH.
The intersegmental muscles (ISMs) of tobacco hornworm, Manduca sexta are a well-characterised model system for examining the biochemical changes that accompany programmed cell death during develop- ment. When the ISMs become committed to die, there are dramatic increases in both the ubiquitin- expression, and ubiquitin-dependent proteolysis. Since the 26S proteasome is responsible for ATP/ubiq- uitin-dependent proteolysis in cells, we examined its enzymatic properties. Specific chymotrypsin-like proteolytic activity of 26S proteasomes isolated from ISM is four times higher than that of surviving flight muscle (FM). However, specific activity does not change between developmental stages within ISM or FM. The difference between proteolytic capacity of the two kinds of muscles is even higher when the ISM become committed to die because 26S proteasome content of ISM increases just before cell death. These observations underline the role of 26S proteasome in programmed cell death.