Homogeneous beta-xylosidases with molecular mass values 120 and 80 kDa (as shown by SDS-PAGE), belonging to the third family of glycosyl hydrolases, were isolated by anion-exchange, hydrophobic, and gel-penetrating chromatography from enzyme preparations based on the fungi Aspergillus japonicus and Trichoderma reesei, respectively. The enzymes exhibit maximal activity in acidic media (pH 3.5-4.0), and temperature activity optimum was 70 degrees C for the beta-xylosidase of A. japonicus and 60 degrees C for the beta-xylosidase of T. reesei. Kinetic parameters of p-nitrophenyl beta-xylopyranoside and xylooligosaccharide hydrolysis by the purified enzymes were determined, which showed that beta-xylosidase of A. japonicus was more specific towards low molecular weight substrates, while beta-xylosidase of T. reesei preferred high molecular weight substrates. The competitive type of inhibition by reaction product (xylose) was found for both enzymes. The interaction of the enzymes of different specificity upon hydrolysis of glucurono- and arabinoxylans was found. The beta-xylosidases exhibit synergism with endoxylanase upon hydrolysis of glucuronoxylan as well as with alpha-L-arabinofuranosidase and endoxylanase upon hydrolysis of arabinoxylan. Addition of beta-xylosidases increased efficiency of hydrolysis of plant raw materials with high hemicellulose content (maize cobs) by the enzymic preparation Celloviridine G20x depleted of its own beta-xylosidase.
Possibilities and limitations of the method of examination of proteolytic enzymes' primary spec ificity by statistical analysis of MALDI (matrix assisted laser desorption/ionization) mass spectra of products obtained by protein substrate proteolysis, without direct determination of their amino acid sequences, were investigated theoretically. The optimum range given by the measurement errors of the peptides' masses for obtaining a statistical set of the events, and the form of statistical data presentation, were chosen. It was shown that the proposed method can be applied only for proteases with a relatively narrow primary specificity (two or three amino acids). The influence of protein substrate molecular weight and amino acid composition on the efficiency of specifics for a particular protease amino acid, revealed under statistical treatment of the set of proteolysis product masses, was studied on the model of trypsin, chymotrypsin, glutamylendopeptidase, pepsin (pH 1.3).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.