Pectic Enzymes and Development of the Pear (Pyrus communis)

Nagel, C. W.; Patterson, M. E.

doi:10.1111/j.1365-2621.1967.tb01316.x

Cited by 55 publications

(25 citation statements)

References 14 publications

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“…Tissue pieces were vacuum-infiltrated with cold (4 C) 100 mm Na-acetate (pH 6.0) containing 0.2% (w/v) Na2S204 and 1% (w/v) Enzyme Assays. PE activity was determined as described by Nagel and Patterson (17) with the aid of an automatic titrating pH meter (Radiometer Titrometer II).…”

Section: Methodsmentioning

confidence: 99%

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Cell Wall Metabolism in Ripening Fruit

Ahmed¹,

Labavitch²

1980

Plant Physiol.

110

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Mature 'Bartlett' pear (Pyras communis) fruits were ripened at 20 C. Fruits at different stages of ripeness were homogenized, and extracts of the low speed pellet (crude cell wall) were prepared. These extracts contained polygalacturonase, pectin esterase, and activity against seven pnitrophenyl glycoside substrates. Polygalacturonase, a-galactosidase, and a-mannosidase increased in activity as the fruit ripened. CeOulase and activities against pear wall xylan and arabinan were absent from the extracts.The changes in cell wall composition which accompany the softening of ripening fruit apparently result from the action of enzymes produced by the fruit. Prominent among the enzymes implicated are PG3 and PE because striking changes in wall pectin content are observed in ripening fruits (1,13,14,21,22), and activities ofthese two enzymes often increase as ripening continues (21). In addition, primarily because of their presence in extracts of ripening fruits, a variety ofglycanases (10,21,26) and glycosidases (3,20,21) have been assigned an unspecified role in fruit cell wall metabolism.This paper describes measurements of the activity of a variety of carbohydrate-degrading enzymes in extracts of ripening 'Bartlett' pears. The potential for depolymerization of pear cell wall polysaccharides was assessed using model substrates containing the same types of glycosidic linkages that have been described for pear cell walls (1). Glycosidase activities were followed using pnitrophenyl substrates. The activities of several enzymes, notably PG, a-mannosidase, and a-galactosidase, increased substantially as the fruit approached the respiratory climacteric. The potential roles of the various enzymes in ripening-associated cell wall modification are discussed. Enzyme Assays. PE activity was determined as described by Nagel and Patterson (17) with the aid of an automatic titrating pH meter (Radiometer Titrometer II). MATERIALS AND METHODSPolysaccharide-degrading activities were followed by measuring the generation of reducing groups according to the method of Nelson (18), as modified by Somogyi (23). The standard reaction mixture contained enzyme and 0.1% (w/v) substrate in I ml of 100 mm Na-acetate (pH 5.0). Incubation was at 37 C. The substrates used were polygalacturonic acid (Sunkist Growers), carboxymethyl cellulose and larch xylan (Sigma), and araban (KochLight Laboratories, Ltd.).Prior to use, the xylan was purified according to the technique of McNeil and Albersheim (as described by Taiz and Honigman [24]) to remove abundant glucose-and mannose-containing contaminants. The araban also had to be treated prior to use in order to remove uronic acid-containing materials. Five g araban were refluxed for 16 h in 250 ml 5 N NaOH containing 4 g NaBH4. The preparation was cooled, neutralized with glacial acetic acid, and centrifuged for 5 min at 1,000g. Final clarification of the supernatant solution was accomplished by filtration through glass fiber (GF/C) paper. The filtrate was dialyzed against 10 mm K-phosphate (pH 7...

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Section: Methodsmentioning

confidence: 99%

“…Enzyme Assays. PE activity was determined as described by Nagel and Patterson (17) with the aid of an automatic titrating pH meter (Radiometer Titrometer II). …”

mentioning

confidence: 99%

Cell Wall Metabolism in Ripening Fruit

Ahmed¹,

Labavitch²

1980

Plant Physiol.

110

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“…Although cellulase activity has been found in a number of ripening fruits (9) including pears (6) its presence in apples has not yet been demonstrated. PG activity has been previously detected in ripe pears (13,22) and was shown to increase during pear ripening (6). Recently, the presence of an exo-PG in apples has been established by us (unpublished data) and other workers (5).…”

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confidence: 97%

Ultrastructural Changes in the Cell Walls of Ripening Apple and Pear Fruit

1979

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Ultrastructural changes in the cell walls of "Calville de San Sauveur" apples (Mahn sylvestris Mi) and "Spadona" pear (Pyrs conunws L.) frit were folowed during rpening. In apple, structural alteratons in cell walls became apparent at advanced stages of softening and showed predominantly disolution of the middle lamella. In pears softening was also associated with the dissolutio of the middle lamella, and in addition a gradual disintegration of fibria material throughout the cell wall. In fully ripe fruit almost al of the frilbar arrangement in the cell wall was lost.Application ofenzyme solutios containig polygalacturonase and cellulase to tissue discs from firm pear fruit led to ultrastructural changes observed in naturally ripening pears. In apple polygalacturonase alone was sufficient to dissolve the middle lamella region of the cell walls, as was also found to occur in naturaly ripening frit. In both apple and pear the cell wall areas containing ploata maintained their structural integrity tbroughout the ripening process. At advanced stages of ripening vesicles appeared in the vicinity of plasmodesmata.A characteristic of the ripening process common to most fruits is a decrease in fruit firmness. Loss in firmness is shown to be associated with the activity of cell wall-degrading enzymes (9, 16) and it is a reasonable hypothesis that this activity could lead to the chemical and structural alterations in cell walls. In an early microscopic study of cell walls from developing apple fruits, no differences were observed in thickness or structure during storage and softening of the fruit (14). Other studies in pear showed that although in lignified walls of stone cells there was no change during fruit maturation, in overripe fruit the parenchymatous cell walls became extremely thin and tenuous (18). Recent studies in avocado (15) also suggested that in softening fruit cell walls lose their structure. In the present work we extend these studies aimed at: (a) using ultrastructural techniques to observe the detailed microscopic changes occurring in the walls of apple and pear, MATERIALS AND METHODS Plant Material. "Calville de San Sauveur" apples (Malus sylvestris, Mill) and "Spadona" pears (Pyrus communis L.) ofuniform size and color were harvested at the mature stage and allowed to ripen at 20 C. Tissue samples from mature and soft apples and pears were then used for the EM2 study. Prior to sampling for EM, the firmness of the fruit was determined with a "Hunter" penetrometer, equipped with an 11. 1-mm tip for apples or a 7.9-mm tip for pears. The tissue firmness of the mature hard apples was from 6.5 to 5 kg and of soft fruit 3.3 kg. In pears the firmness at the mature hard stage was 7 kg and in soft fruit 2.5 kg.Ultrastructural studies were also made on fruit discs treated with applied enzymes. Small discs, 1-cm diameter, 3 mm thick, from mature hard fruit were incubated for 1 to 2 h in acetate buffer solutions containing commercial enzyme preparations. The enzyme solutions consisted of 25 mg/ml tomat...

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“…PE in the supernatant was assayed by acid-base titration according to Nagel and Patterson. 18 By definition, one unit of enzyme activity was equivalent to the amount of enzyme catalyzing the formation of 1 µmol ester hydrolysed per minute per gram of the original fresh weight of the pear flesh.…”

Section: Enzyme Extraction and Assaymentioning

confidence: 99%

Effects of cushioning materials on the firmness of Huanghua pears (Pyrus pyrifolia Nakai cv. Huanghua) during distribution and storage

Zhou

2007

Packag Technol Sci

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The type and quality of cushioning materials could significantly affect the vibration intensity and physical quality of fruits during transport. In the current paper, we evaluated the different cushioning materials (paper-wrap materials, foam-net packages) for their protective effect on the vibration levels, number of bruises and mechanical damage to Huanghua pears (Pyrus pyrifolia Nakai cv. Huanghua) during transport. Changes in pear firmness, hydrolase activity and cell wall constituents were examined in fruits stored for up to 36 days after transport. Our data suggested that the choice of cushioning material significantly reduced the vibration intensity in transit, affecting the physical quality of fruits and their subsequent commercialization, and that foam-net packages provided a greater protective effect than paper-wrap packages.

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Pectic Enzymes and Development of the Pear (Pyrus communis)

Cited by 55 publications

References 14 publications

Cell Wall Metabolism in Ripening Fruit

Cell Wall Metabolism in Ripening Fruit

Ultrastructural Changes in the Cell Walls of Ripening Apple and Pear Fruit

Effects of cushioning materials on the firmness of Huanghua pears (Pyrus pyrifolia Nakai cv. Huanghua) during distribution and storage

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