Isoelectric focusing in thin layer polyacrylamide gel combined with a zymogram method for detecting enzyme microheterogeneity: sample application

Evidence for phospholipase B activity in Fusobacterium necrophorum cultures and its association with hemolysin/leucocidin activities

Phospholipase B (PLB) activity was present in Fusobacterium necrophorum cultures and it correlated closely with virulence and co-purified with the hemolysin/leucocidin activities. All three activities were associated with a large molecule or molecular complex (6 x 10(2)-2 x 10(3) kDa) exhibiting varying degrees of aggregation. These were present mainly in the culture medium and to a lesser extent in cell sonicates. The PLB and toxin activities were sensitive to heat, dissociating agents, proteolytic enzymes, prolonged purification regimes, freeze-drying and repeated freeze-thawing. The toxin(s) were stable over a broad range of pH, did not require divalent ions or reducing agents and could be kept for several months as an ammonium sulfate precipitate at 4 degrees C, or stored as a concentrated liquid in the presence of proteolytic inhibitors at - 20 degrees C.

Purification and characterization of a ribonuclease from Aspergillus giganteus IFO 5818, the gigantin. Immunological and enzymic comparison with alphasarcin

A protein has been isolated from a culture medium of Aspergillus giganteus IFO 5818 (gigantin) and purified by ion-exchange chromatography successively on DEAE-cellulose and carboxymethyl-cellulose, and gel-filtration chromatography on Biogel P10. With a high purity, gigantin was found to be a non-glycosylated basic protein with a relative molecular mass of 17000 +/- 200 determined in PAGE/SDS. Gigantin was able to digest the synthetic homopolymers of nucleic acids poly(A), poly(I), poly(C) and poly(U). The catalytic action has an optimal pH around 7.0, an optimal temperature at 45-55 degrees C and can be inhibited by cations. Gigantin activity, analyzed as its capacity to hydrolyze RNA from yeast, was comparable to that of alphasarcin, a similar biochemical protein produced by the strain A. giganteus MDH 18894. A study of the substrate specificity for alphasarcin indicated a preference for poly(A) and poly(I), while gigantin had greater activity on poly(C) and poly(U). The cross reaction of gigantin with a rabbit antiserum to alphasarcin suggests a high sequence similarity between both proteins. However, gigantin is immunologically distinguishable from alphasarcin as alphasarcin antiserum detects epitopes in alphasarcin that are not present in gigantin.

Phospholipase C from Clostridium perfringens: preparation and characterization of homogeneous enzyme

A new procedure for the purification of phospholipase C from Clostridium perfringens has been devised that results in essentially pure enzyme. The procedure consists of ammonium sulfate fractionation, ion-exchange chromatography on QAE-Sephadex, and affinity chromatography on phosphatidylcholine linked to Sepharose. The molecular weight of the enzyme, determined by sodium dodecyl sulfate-gel electrophoresis, amino acid analysis, and gel filtration, is 43,000; and the isoelectric point is pH 5.4. The enzyme was optimally active with phosphatidylcholine dispersed in sodium deoxycholate, although appreciable activity was observed with either phosphatidylcholine or sphingomyelin dispersed with ethanol. The requirement for metal ions in the assay could be met by a number of different ions. The pure enzyme was found to contain 2 mol zinc per mol enzyme, thus implicating it as a zinc metalloenzyme.

Quantitative assay of deoxyribonuclease activity after isoelectric focusing in polyacrylamide gels: pH control and effects of enzyme diffusion

A method for the quantitative assay of nuclease activity in crude cell lysates after isoelectric focusing (IEF) in polyacrylamide slab gels is described. After IEF, an agarose overlay gel containing DNA is placed on the IEF gel and the nuclease activity quantified by the loss of ethidium bromide fluorescence of the DNA. With this method a linear response was obtained for 1 to 10 ng of DNase I. Various methods of pH equilibration after IEF were also evaluated. The use of a high buffer concentration in the overlay gel is recommended to control the pH during the enzyme reaction. An analytical solution for the diffusion of enzymes from the IEF gel to the overlay gel is also presented and an equation that may be used to choose optimum times for transfer of the enzyme from the IEF gel to the overlay gel is given.

Human prostatic acid phosphatase: properties of the native enzyme, and the enzyme-antibody complex

Acid phosphatase purified from human prostatic tissue was shown to be homogeneous by polyacrylamide gel electrophoresis and N-terminal amino acid analysis. However, isoelectric focusing revealed a large number of isoenzymes which were reduced to four by digestion with neuraminidase. It is suggested that the patterns observed are due to differences in bound carbohydrate attached to the same protein backbone. Antiserum to the purified enzyme was produced in rabbits and reacted with the enzyme to form an enzymatically active complex of large molecular weight. This complex is more stable at high temperatures than the native enzyme. Kinetic analysis of both the enzyme and the enzyme-antibody complex demonstrated that the binding of the antibody caused no significant change to the active site of the enzyme.

Influence of calcium binding on the thermal stability of 'thermitase', a serine protease from Thermoactinomyces vulgaris

'Thermitase' (EC 3.4.21.14), a thermostable extracellular serine protease from Thermoactinomyces vulgaris, binds one calcium ion with a dissociation constant of about 10-4M at 25 degrees C and pH 7.5 to 3.5. In addition, two calcium ions are bound more tightly to the enzyme, as shown by experiments with a calcium-selective electrode. The single most weakly bound calcium ion causes a slight quenching of the protein fluorescence emission, accompanied by a stabilization against thermal denaturation or autolysis and an increase of esterolytic activity of approx. 10%. The tightly bound calcium ions have only a slight influence on activity or on thermal denaturation or autolytic degradation. The activation parameters of thermal denaturation indicate that 'thermitase' belongs to the class of thermostable enzymes with a high intrinsic stability.

Comparison of the properties of the alcohol dehydrogenases from wild-type and mutant Chinese hamster somatic cells

Alcohol dehydrogenases (alcohol: NAD oxidoreductase, E.C. 1.1.1.1.) from allyl alcohol-resistant and wild-type Chinese hamster cells were purified using gel filtration, ion-exchange, and affinity-column chromatography. Both enzymes exhibited the same isozyme band patterns on electrophoresis and isoelectric focusing. Physicochemical properties of the two enzymes such as pH and temperature optima, Km values, and temperature stability were found to be the same within the experimental errors. The genetic significance of these findings is discussed.

Improved procedure of purification of inorganic pyrophosphatase from Bacillus stearothermophilus

An improved method for isolation of inorganic pyrophosphatase (EC 3.6.1.1) from Bacillus stearothermophilus is described. The enzyme was purified to more than 90% after two chromatographic steps. A molecular weight of 140,000 daltons was estimated by density gradient centrifugation. The isoelectric point was found to be 4.0.

New procedure for concentration and analytical isoelectric focusing of proteins

Proteins in aqueous salt solutions (up to 4 mil) were adsorbed by hydrophobic interaction on phenyl-Sepharose gel (0.1 ml) in small columns. After washing out excess salt, gels were applied on the surface of flat bed polyacrylamide gels for isoelectric focusing, which resulted in efficient desorption and transport of protein out of the phenyl-Sepharose gel. There was no difficulty in obtaining a fifty-fold concentration. The following parameters at adsorption of protein were studied: (i) salt concentration in the protein solution; (ii) phenyl-Sepharose gel adsorptive capacity for protein; (iii) suitable volume of washing solution for the phenyl-Sepharose gel. Theoretical aspects on factors promoting adsorption and desorption of proteins on phenyl-Sepharose gel are discussed. Also discussed are earlier used procedures for concentration and/or dialysis. When dilute protein solutions are to be examined for analytical purposes, the proposed procedures seems to be a valuable aid, which does not require expensive equipment, and is quick and simple to perform.