In pectinesterase

Termote, F. Rombouts, F. M. Pilnik, W. Stabilization of cloud in pectinesterase active orange juice by pectic acid hydrolysates. J. Food Biochem., 1977, 1, 15-34. 

Termote, F., Rombouts, F.M., Klnik, W. Stabilization of cloud in pectinesterase active orange juice by pec-tic acid hydrolysates. J. Food Biochem. 1,15 (1977) Teuber, M. Production of chymosin (EC 3.4.23) by microorganisms and its use for cheesemaldng. Int. Dairy Federation, Ann. Sessions Copenhagen 1989, B-Doc 162... 

Expression of polygalacturonase and pectinesterase in normal and transgenic tomatoes. 

Figure 2 Pectinesterase activity in transgenic tomato finit. Activity is expressed as...

Figure 1. Pectinesterase activity in normal tomato fruit. Enzyme activity is exjM-essed as (ueq min gfwt)...

Hobson, G.E. (1963) Pectinesterase in normal and abnormal tomato finit. Biochemical Journal. 86. 358-365. 

Pressey,R and Avants,J.K (1972) Multiple forms of pectinesterases in tomatoes. Phytochemistry. 11. 3139-3142. 

Tucker,G. A.,Robertson,N.G. and Grierson,D. (1982) Purification and changes in activities of tomato pectinesterase isoenzymes. Journal of the Science of Food and Agriculture. 33. 396-400. 

Cations Increase Activity and Enhance Permeation of Pectinesterase in Ultrafiltration... 

The effect of pH and cation concentration on pectinesterase (PE) activation and permeation on 30 kD MWCO ultrafiltration (UF) membrane was evaluated. In order of increasing effectiveness, PE activity was stimulated by monovalent and divalent cations, poly amines and trivalent cations. A similar trend was observed for permeation on UF membranes. Cation addition and higher pH releases PE from an inactive complex, increases activity, and increases permeation. Higher cation concentration decreases activity and permeation. These results suggest a common mechanism is involved in PE activation and permeation. 

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. 

Evans, R. McHale, D. 1968. Multiple forms of pectinesterase in limes and oranges. Phytochemistry 17 1073-1075. 

Macdonald, H.M. Evans, R. Spenser, W.J. 1993. Purification and properties of the major pectinesterases in lemon fruits (Citrus limon). J. Sci. Food Agric. 62 163-168. 

Rouse, A.H. 1951. Effect of insoluble solids and particle size of pulp on the pectinesterase activity in orange juice. R. State Hort. Soc. Proc. 64 162-166. 

Rouse, A.H. 1953. Distribution of pectinesterase and pectin in component parts of citrus fruits. Food Technol. 7 360-362. 

Rouse, A.H. Atkins, C.D. 1955. Pectinesterase and pectin in commercial orange juice as determined by methods used at the Citrus Experiment Station. Florida Agric. Exper. Station Bull. 570 1-19. 

The activities of pectic enzymes present in cultivation medium (98 mg of protein extracted from 2.5 1 of pectin medium) were poor, not leading to the clarification of cultivation medium indicating the cleavage of pectate chains, with values 0.024 pmol/min.mg for polygalacturonase, 0.004 pmol/min.mg for exopolygalacturonase, 0.034 pmol/min.mg for pectinesterase and 0.005 pmol/min.mg for pectin lyase. The production of individual pectic enzymes was dependent on the C-source used in the cultivation medium (Tab. 1). 

Data on the pectin content of the initial material (AUAC and DE) is presented in Table 1. It is evident that the main difference between the two lots of oranges was in their anhydrouronic acid content. Observations from previous research (1) were confirmed that microwave heating of the fresh material ensured better drying conditions by inactivating pectolitic enzymes, particularly pectinesterase. Thus a better retention of the degree of esterification of pectin was ensured. 

Properties of pectinesterase from Penicillium fellutanum Biourge and new developments in pectin applications... 

Some properties of Penicillium fellutanum pectinesterase were studied. The optimum of pectinesterase action was detected at pH 5 and 45 °C. The enzyme was stable at pH 4 — 5 and 40 °C (pH 5) for 240 min. and was specific towards lemon pectin. An enzyme preparation composed mainly of pectinesterase was partially purified by gel filtration. Pectinesterase activity was accumulated in one of the obtained fractions. Molecular weights of fraction determined were found to be 46,000 and 1,200. Disk electrophoresis in polyacrilamide gel of the purified preparation revealed two protein bonds with one active component. The partially purified enzyme had the kinetic characteristics =... 

Miller and Macmillan [4] carried out purification of pectinesterase from Fusarium oxysporum f. sp. vasinfectum culture fluid (fivefold degree of purification). According to the obtained data the purified enzyme possessed very low polygalacturonatlyase one. Disk electrophoresis at pH 4.3 revealed two protein components. The authors did not study distribution of pectinesterase activity in these components. Molecular weight of fungal pectinesterase determined using gel — filtration on Sefadex G — 75 was found to be 35,000. 

Enzymatic preparation with predominant content of pectinesterase (obtained from Penicillium fellutanum culture liquid by isolation by acetone was purified. Primary enzymatic preparation was re — precipitated by three volumes of ethyl alcohol and centrifuged (6000 rev/min.) during 20 min. The obtained precipitate of partially purified pectinesterase preparation was dried in vacuum — desiccator. Sephadexes G — 50, G-75, G-lOO, G-200 "LKB" (Sweden) and Toyopearl HW-55 (Japan) were used for separation of enzymatic complex by gel — filtration. 

Molecular weight of the components of the enzymatic complex was determined using a Sephadex G —75 column after its calibration by dextrans with molecular weight equal to 10,000, 40,000 and 70,000 and rafinose with molecular weight of 504. Fractions were also analyzed by the disk —electrophoresis method in PAAG (7) using 7.5% polyacrilamide gel (pH 4.3). Activity of pectinesterase was determined by titrometric method [8]. The enzymatically released methanol analyzed by gas—liquid chromatography [9]. 

Study of the temperature optimum of pectinesterase activity showed, that peak of pectinesterase activity was observed at the temperature equal to 45 °C. It is shown on Figure 1 that pectinesterase was stable at pH 4 — 5. At pH 2 activity of the enzyme reduced by 25% in 60 min., at pH 3 and pH 6 it decreased by 6 — 8%. At pH 8 the activity decreased by 90.7% during the same time. At pH 9 the enzyme activity was inactivated during 15 min. 

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