Kvetoslava Heinrichová

An exopectate lyase of Butyrivibrio fibrisolvens from the bovine rumen.

An extracellular pectinolytic enzyme produced by Butyrivibrio fibrisolvens isolated from the bovine rumen was studied. The enzyme had a pH optimum of 8.0 to 8.5 and was stimulated by Ca2+ and inhibited by EDTA. The products of pectinolysis had an absorption peak at 235 nm and reacted with thiobarbituric acid, indicating a lyase type of action. The enzyme cleaved the substrates terminally from the reducing end; action on poly- and oligogalacturonates resulted in the formation of an unsaturated trigalacturonate. The enzyme was classified as an exopectate lyase (EC 4.2.2.9). A pectinesterase was also produced by B. fibrisolvens but polygalacturonase was not detected.

Induction and Inducers of the Pectolytic System in Aureobasidium pullulans

Abstract. The strain of Aureobasidium pullulans NRRL Y-2311 (CCY 27-1-98), known as a hyperproducer of endo-1,4-β-xylanase, exhibited good growth on pectin or pectate. Growth on these carbon sources is associated with an inducible production of significant amounts of pectolytic enzymes, of which exopolygalacturonase (EC 3.2.1.67) and endopolygalacturonase (EC 3.2.1.15) were identified. The two enzymes are not produced on D-glucose or under carbon starvation conditions. The enzymes can be induced in glucose-grown cells by D-galacturonic acid and its oligomers. Thus, D-galacturonic acid, the monomer derived from the polysaccharide, appears to be the natural inducer or a precursor of an inducer of pectolytic enzymes in the studied yeast.

A polygalacturonate lyase produced by Lachnospira multiparus isolated from the bovine rumen.

A poly(1,4-alpha-D-galacturonide) lyase (EC 4.2.2.2) from the culture fluid of Lachnospira multiparus was purified about 20-fold. The optimum pH and temperature for enzyme activity were 8.0 and 40 degrees C. The enzyme required Ca2+ and was inhibited by EDTA; it preferred polygalacturonate as substrate, cleaving 1,4-alpha-glycosidic linkages randomly to form unsaturated galacturonates, mainly the unsaturated digalacturonate. Some properties of the crude and purified enzyme preparations are described. An exopolygalacturonase is also produced by this organism.

Purification and characterization of an extracellular exo-d-galacturonanase of Aspergillus niger

A D-galacturonanase (EC 3.2.1.67) catalyzing the degradation of D-galacturonans by terminal action pattern was purified from a culture filtrate of Aspergillus niger by a procedure including the salting-out with ammonium sulfate, precipitation by ethanol, chromatography on DEAE-cellulose, and gel chromatography on Sephadex G-100. The obtained preparation was slightly contaminated by an enzymically inactive protein fraction. Maximum activity and stability of the enzyme was observed at pH 5.2. The enzyme degrades digalacturonic acid, p-nitrophenyl-alpha-D-galactopyranuronide, as well as oligogalacturonides containing at the nonreducing end 4-deoxy-L-threo-hexa-4-enopyranosyluronate. It differs from all A. niger enzymes so far described which degrade D-galaturonans by the terminal action pattern, in not clearly preferring low-molecular substrates. It is therefore classified as an exo-D-galacturonanase.

An exo-D-galacturonanase of Butyrivibrio fibrisolvens from the bovine rumen.

An intracellular pectinolytic enzyme was isolated from a cell extract of Butyrivibrio fibrisolvens and purified. The optimum pH for enzyme activity was 5.6. The enzyme preferentially degraded de-esterified substrates by hydrolysis of monosaccharide units from the non-reducing end; the only product of degradation was D-galacturonic acid. Values of Km and Vmax for oligo- and polygalacturonates indicated that the best substrate was digalacturonic acid; oligogalacturonates containing either a saturated or a delta 4,5-unsaturated non-reducing end were both degraded. The enzyme was classified as an exo-D-galacturonanase [poly(1,4-alpha-D-galacturonide) galacturonohydrolase (EC 3.2.1.67)].

Chromogenic substrate for endo-polygalacturonase detection in gels

Abstract A simple, sensitive zymogram technique for the detection of endo-polygalacturonase (EC 3.2.1.15) in gel slabs after electrophoresis or isoelectrofocusing was developed. This technique employs a new chromogenic substrate prepared by coupling D -galacturonan DP 10 with Ostazin Brilliant Red S-5B dye. The detection of multiple forms of endo-polygalacturonase is based on the selective removal of depolymerized dyed substrate from the agar replicas by a solvent system that does not solubilize non-degraded dyed D -galacturonan DP 10 present in agar gel replicas.

Mechanism of action of d-galacturonan digalacturonohydrolase of Selenomonas ruminantium on oligogalactosiduronic acids

The mechanism of action of the specific D-galacturonan digalacturonohydrolase [poly-(1----4)-alpha-D-galactosiduronate digalacturonohydrolase, EC 3.2.1.82] of Selenomonas ruminantium was investigated by using reducing-end [1-3H]-labeled oligogalactosiduronates having degree of polymerization 3-5 as the substrates. The reaction products, incorporation and distribution of radioactivity in products, and the frequency of oligogalactosiduronate bond-cleavage were quantitatively estimated as functions of the substrate concentration. An alternative cleavage of tri(D-galactosiduronate) occurred during the enzyme reaction, indicating the participation of some bimolecular mechanism in addition to unimolecular hydrolysis in the action of the enzyme. Unimolecular hydrolysis takes place at low initial concentration of the substrate. The shifted termolecular enzyme-substrate complex formation and the subsequent galactosyluronic transfer is the predominant mechanism in degradation of tri(D-galactosiduronate) at high concentration. Tetra(D-galactosiduronate) and penta(D-galactosiduronate) are degraded by unimolecular hydrolysis at low, as well as high concentration of the substrate.

D-Galacturonandigalacturonohydrolase covalently bound on to a polyacrylamide-type support

d‐Galacturonandigalacturonohydrolase was immobilized by covalent coupling on to a polyacrylamide‐type carrier BIO Gel CM100, activated by water‐soluble carbodiimide. Catalytic properties, stability and action pattern of the immobilized enzyme are reported.