Pectinesterases assay

Thermostable pectinesterases (TSPE), operationally defined as activity that survives 5 min at 70°C, contribute most to cloud loss in juices at low temperatures and juice pH (26). The percentage of total activity that is thermostable is highly variable and differs in kinetic properties, (22, 26), ease of solubilization (28, 29), stability to low pH (25) and stability to freeze-thaw cycles (23). Some of the variability in reported total PE and TSPE may be related to limitations of current methods to quantify activity. Any processing treatment or assay condition that increases cell wall breakdown or release PE from a pectin complex would enhance detection of total and TS-PE activity. Commercially, PE is inactivated by pasteurization in a plate heat exchanger or during concentration in the TASTE evaporator. 

During a study of the biosynthesis of pectin substances, a sensitive micromethod for the assay of pectinesterase activity was developed111 that uses a biosynthetically prepared [14C] methyl-labelled pectin as the substrate after enzymic de-esterification, the substrate remaining is precipitated with an excess of methanol and, after centrifugation, the [14C]methanol present in the supernatant liquor is counted in a liquid scintillation counter in order to assess the pectinesterase activity. 

Qualitative tests for the presence of pectinesterase, based on a color change of such indicators as Bromothymol Blue or Bromocresol Green, after de-esterification of pectin, are simple and very useful these tests are used as drop tests when checking chromatographic columns85,97 100 or for a qualitative assay of pectinesterase in culture filtrates, using the cup-plate method.113... 

PGase activity assay, 335-348 values for acetylation and methylation in some foods, 743 (table) Pectinesterase (PE), characterized, 342 PEG-palmitate, synthesis of, 308 Peptidases, see also Proteinases activity assays... 

CN 06897, and Rohm Tech Inc., Malden, MA 02148. All preparations were assayed for polygalacturonase (PG), cellulase, and pectinesterase (PE) activities by the methods of Vas, et al. (6 ) as modified by Bruemmer et al. ( ] ). PG and cellulase activities were determined by reduction of specific viscosity in an Ostwald-type viscosimeter held in a 50°C water bath. PG activity was measured on both 1.5% polygalacturonic acid (U.S. Biochemical Corp.), titrated... 

A review of the occurrence, purification, properties, and modes of action of hemicellulases has dealt with L-arabinanases, D-galactanases, D-mannanase, and D-xylanases, while a comprehensive review of pectolytic enzymes has discussed their classification and the assay and properties of pectinesterases and poly-D-galacturonate hydrolases and lyases. ... 

Nucieotidases.—Since the 5 -nucleotidase from Dictyostelium discoideum interacted with immobilized concanavalin A, it appears to be a glycoprotein. Pectinesterases.—The occurrence, formation, assay, purification, and specificities of pectinesterases have been reviewed. Pectinesterase activity was detected both in healthy and diseased onions Allium cepa), but not in cultures of the invading bacterium (Pseudomonas cepacia) Both the pectinesterase and poly-D-galact-uronate lyase activities of Clostridium multifermentans are associated with a single complex. ... 

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