scholarly journals Phenylalanine Ammonia-lyase Inhibitors Do Not Prevent Russet Spotting Lesion Development in Lettuce Midribs

1998 ◽  
Vol 123 (4) ◽  
pp. 687-691 ◽  
Author(s):  
Galen Peiser ◽  
Gloria López-Gálvez ◽  
Marita Cantwell ◽  
Mikal E. Saltveit
Keyword(s):  
Phenolic Compounds ◽  
Phenylalanine Ammonia Lyase ◽  
Phenylpropanoid Pathway ◽  
Aminooxyacetic Acid ◽  
Physiological Disorder ◽  
Phenolic Metabolism ◽  
Pal Activity ◽  
Iceberg Lettuce ◽  
Tartaric Acids ◽  
Lyase Activity

Russet spotting is a physiological disorder of lettuce (Lactuca sativa L.) caused by exposure to hormonal levels (<1 μL·L-1) of ethylene in air at ≈5 °C. Enhanced phenolic metabolism and the accumulation of phenolic compounds accompany the appearance of brown, oval lesions on the leaf midrib. Phenylalanine ammonia-lyase (PAL) is the first committed enzyme in the phenylpropanoid pathway. Three inhibitors of PAL activity [2-aminoindan-2-phosphonic acid (AIP), α-aminooxyacetic acid (AOA), and α-aminooxi-β-phenylpropionic acid (AOPP)] greatly reduced the accumulation of phenolic compounds and browning of lesions. At a concentration of 50 μm, AIP inhibited the formation of chlorogenic and dicaffeoyl tartaric acids in cut midribs of iceberg lettuce by 92% and 98%, respectively. AIP competitively inhibited PAL activity from a lettuce midrib homogenate with an apparent Ki of 22 nm. While the formation of phenolic compounds was strongly inhibited by AIP, the number of lesions associated with russet spotting was not affected. Only the color of the lesions was affected by AIP. In control midribs the russet spotting lesions were brown while those in the AIP-treated midribs were initially olive green and after 3 to 7 days these lesions turned the characteristic brown color. No tyrosine ammonia-lyase activity was detected in a homogenate of lettuce midrib tissue. These results indicate that the early development of russet spotting lesions is independent of the increase in PAL activity and phenolic compounds rather than an effect of these increases as previously suggested. However, accumulation of phenolic compounds does contribute to the subsequent browning symptoms indicative of russet spotting.

scholarly journals Effects of Temperature on Ethylene-induced Phenylalanine Ammonia Lyase Activity and Russet Spotting in Harvested Iceberg Lettuce

1995 ◽  
Vol 120 (1) ◽  
pp. 84-87 ◽  
Author(s):  
M.A. Ritenour ◽  
M.J. Ahrens ◽  
M.E. Saltveit
Keyword(s):  
Phenolic Compounds ◽  
Phenylalanine Ammonia Lyase ◽  
Rapid Decrease ◽  
Effect Of Temperature ◽  
Pal Activity ◽  
Iceberg Lettuce ◽  
Lyase Activity ◽  
Lag Period ◽  
Effects Of Temperature ◽  
Phenylalanine Ammonia Lyase Activity

Experiments were conducted to study the effect of temperature on the ethylene inducibility of phenylalanine ammonia lyase (PAL, EC 4.3.1.5) activity and the development of russet spotting (RS) in Iceberg lettuce (Lactucu sutiva L.). Tissue exposed to ethylene and held at 15 or 20C showed earlier hut lower peaks in PAL activity than tissue held at 5C. Accumulation of total soluble phenolic compounds, and the development of RS paralleled increases in PAL activity after a short lag period. Lettuce tissue transferred from 5 to 15C after 1 to 3 days showed later hut higher peaks in PAL activity than tissue continuously held at 15C. Transferring ethylene-exposed tissue to 0C before RS symptoms developed greatly limited further rise in PAL activity and RS development. Discontinuing ethylene exposure after 4 days resulted in a rapid decrease in PAL activity. Lettuce tissue exposed to ethylene for 4 days and then transferred from 5 to 0C after the development of moderate RS symptoms showed no difference in RS after 8 days compared to tissue stored continuously at 5C.

scholarly journals Monitoring of the PAL Enzymatic Activity and Polyphenolic Compounds in Leaves and Fruits of Two Myrtle Cultivars during Maturation

Agriculture ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 389
Author(s):  
Silvia Medda ◽  
Leonarda Dessena ◽  
Maurizio Mulas
Keyword(s):  
Phenolic Compounds ◽  
Phenylalanine Ammonia Lyase ◽  
Raw Materials ◽  
Phenylpropanoid Pathway ◽  
Polyphenolic Compounds ◽  
Antioxidant Compounds ◽  
Total Polyphenols ◽  
Spectrophotometric Methods ◽  
Pal Activity ◽  
Potential Use

The leaves and berries of myrtle (Myrtus communis L.) are rich in phenolic compounds, such as phenolic acids, flavonoids, and flavanols. The richness of these antioxidant compounds allows the potential use of myrtle biomasses as raw materials for medicinal and functional food products. Most of the phenolic compounds originate from the phenylpropanoid pathway, where phenylalanine ammonia lyase (PAL) enzyme activates the first step. The objective of this research is to study the activity of PAL as related to accumulation in the myrtle fruits and leaves of some phenolic compounds in the period between blossom and full berry ripening. With this aim, we compared two model genotypes with different fruit coloration. In leaves and berries of two cultivars, ‘Giovanna’ with pigmented berries and ‘Grazia’ with white berries, the PAL activity and content of polyphenols, anthocyanins, flavonoids, and tannins were determined with spectrophotometric methods. PAL activity was quite constant in leaves and variable in berries: Greater in berries of ‘Giovanna’ than in those of ‘Grazia’ cultivar, and increasing from berry color-break to full ripening. In berries, a positive correlation between PAL and flavonoids (r = 0.44), and between PAL and anthocyanins (r = 0.69), as well as a negative correlation between PAL and total polyphenols (r = −0.471), were found.

scholarly journals EFFECT OF TIME/TEMPERATURE TREATMENTS ON PHENYLALANINE AMMONIA-LYASE ACTIVITY AND DEVELOPMENT OF RUSSET SPOTTING IN ICEBERG LETTUCE

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1127c-1127
Author(s):  
M.A. Ritenour ◽  
M.E. Saltveit ◽  
M.J. Ahrens
Keyword(s):  
Phenylalanine Ammonia Lyase ◽  
Phenolic Content ◽  
Subjective Evaluation ◽  
Pal Activity ◽  
Iceberg Lettuce ◽  
Lyase Activity ◽  
Highly Correlated ◽  
Phenylalanine Ammonia Lyase Activity ◽  
Kinetics Of ◽  
Practical Implications

Russet spotting (RS) is an important postharvest disorder in Iceberg lettuce (Lactuca sativa L.). Previous studies showed that RS is induced by exposure to ∼5 ppm (ul/l) ethylene at ∼5C for 3 days and is characterized by the appearance of 1 to 2 mm diam. oval, brown sunken spots along the midrib. Increases in phenylalanine ammonia-lyase (PAL) activity and phenolic content are highly correlated with RS development. Ethylene-induced PAL activity is much less at higher (12C) or lower (0C) temperatures. In this study isolated whole leaves were exposed to a log series of ethylene concentrations from 0.1 to 10 ppm at temperatures from 0.0C to 20C for up to 8 days. Tissue was transferred among these various treatments to investigate the kinetics of PAL induction, activity and deactivation, phenolic accumulation, and RS development. A subjective evaluation was then made of RS development using a 1 to 9 scoring system in which 1 was no RS, and then PAL activity and phenolic content were measured. Preliminary results indicate that ethylene-induced PAL activity was decreased more rapidly upon transfer to temperatures above 10C than to 0.0C. Accumulation of phenolic compounds and development of RS paralleled each other, and were positively related to PAL activity. Practical implications of these results will be discussed.

scholarly journals Effect of Intensity and Duration of Heat-shock Treatments on Wound-induced Phenolic Metabolism in Iceberg Lettuce

1997 ◽  
Vol 122 (6) ◽  
pp. 873-877 ◽  
Author(s):  
Julio G. Loaiza-Velarde ◽  
Francisco A. Tomás-Barberá ◽  
Mikal E. Saltveit
Keyword(s):  
Phenolic Compounds ◽  
Heat Shock ◽  
Chlorogenic Acid ◽  
Tartaric Acid ◽  
Phenylpropanoid Metabolism ◽  
Minimal Processing ◽  
Subsequent Increase ◽  
Phenolic Metabolism ◽  
Pal Activity ◽  
Iceberg Lettuce

Wounding during minimal processing of lettuce (Lactuca sativa, L.) induces alterations in phenolic metabolism that promote browning and the loss of quality. The activity of phenylalanine ammonia-lyase (PAL; the first committed enzyme in phenylpropanoid metabolism) and the concentration of phenolic compounds (e.g., chlorogenic acid, dicaffeoyl tartaric acid, and isochlorogenic acid) increase in excised iceberg lettuce midrib segments after wounding. The effect of short heat-shock treatments on browning and phenolic metabolism in excised midrib segments of iceberg lettuce was studied. As the heat-shock temperature increased from 20 to 70 °C, there was a decrease in the subsequent increase in PAL activity and the accumulation of phenolic compounds in excised midrib segments. Treatments of 45 °C for 120 s, 50 °C for 60 s, or 55 °C for 30 s significantly reduced the increase in PAL activity and subsequent browning seen in control tissue after wounding. Exposure to 45 °C for 480 s, 50 °C for 60 s, or 55 °C for 45 s prevented PAL activity from rising above initial levels. Phenolic compounds remained at initial levels for 3 days in excised midribs exposed to 50 °C for 90 s or to 55 °C for 60 s. However, 55 °C damaged the tissue, as indicated by a* and L* Hunter color values. The synthesis of chlorogenic acid, dicaffeoyl tartaric acid, and isochlorogenic acid was greatly reduced by these heat-shock treatments. These treatments also decreased polyphenol oxidase activity and, to a lesser extent, peroxidase activity.

scholarly journals Effects of α-aminooxyacetic acid on the level of polyamines, anthocyanins and photosynthetic pigments in seedlings of common buckwheat (Fagopyrum esculentum Moench)

2011 ◽  
Vol 80 (2) ◽  
pp. 99-104 ◽  
Author(s):  
Marcin Horbowicz ◽  
Ryszard Kosson ◽  
Danuta Koczkodaj ◽  
Lesław B. Lahuta
Keyword(s):  
Photosynthetic Pigments ◽  
Phenylalanine Ammonia Lyase ◽  
Fagopyrum Esculentum ◽  
Aminooxyacetic Acid ◽  
Common Buckwheat ◽  
Total Carotenoids ◽  
Pal Activity ◽  
Lyase Activity ◽  
Phenylalanine Ammonia Lyase Activity ◽  
Fagopyrum Esculentum Moench

The present paper discusses the effects of α-aminooxyacetic acid (AOA) on contents of polyamines, anthocyanins, photosynthetic pigments and phenylalanine ammonia-lyase activity in seedlings of common buckwheat (<em>Fagopyrum esculentum</em> Moench). AOA clearly decreased light-induced formation of anthocyanins and inhibited PAL activity in buckwheat hypocotyls, although a slight stimulatory effect on anthocyanins content in buckwheat cotyledons was observed. AOA declined the contents of chlorophylls <em>a</em> and <em>b</em> and total carotenoids in buckwheat cotyledons. The results show that AOA inhibits phenylpropanoids biosynthesis in buckwheat hypocotyls, and suppress photosynthesis in cotyledons. Moreover, the experiments show that AOA enhances the level of free putrescine in hypocotyls and the level of spermidine in buckwheat cotyledons. AOA also diminished the content of putrescine in cotyledons, but did not affect its level in buckwheat hypocotyls. AOA also substantially declined the level of cadaverine in buckwheat cotyledons, and did not affect its content in hypocotyls. Differences in effect of AOA on anthocyanins and polyamines accumulation indicate various physiological roles of the compounds in buckwheat hypocotyls and cotyledons.

scholarly journals PHENOLIC METABOLISM AND INTERNAL BREAKDOWN (CHILLING INJURY) OF PEACH FRUIT

HortScience ◽  
1990 ◽  
Vol 25 (11) ◽  
pp. 1356H-1357 ◽  
Author(s):  
Hendrik van Gorsel ◽  
Adel A. Kader
Keyword(s):  
Phenolic Compounds ◽  
Phenylalanine Ammonia Lyase ◽  
Chilling Injury ◽  
Limiting Factor ◽  
Stone Fruits ◽  
Peach Fruit ◽  
Phenolic Metabolism ◽  
Pal Activity ◽  
Postharvest Handling ◽  
Chilling Temperatures

Internal breakdown (IB) is the limiting factor in the storage and postharvest handling of stone fruits. The symptoms of IB appear when fruits are kept for prolonged periods at temperatures below 10C and include leatheriness, mealiness, browning and bleeding of the flesh, and failure to ripen normally. We investigated the changes in phenolic compounds associated with IB of stone fruits. Twenty-eight phenolic compounds were separated by HPLC. Ten of these components were significantly affected by chilling temperatures. The concentration of six phenols changed in response to ripening after chilling temperatures, parallel to the appearance of IB symptoms. Most phenols showed a concentration gradient from the inside to the outside of the fruit, Comparison between peach cultivars showed characteristic differences in phenol metabolism during ripening. In both cultivars the most predominant phenol, chlorogenic acid, showed little change in concentration during storage. The structure of key phenolic compounds will be determined in order to elucidate the biochemical relationship between the phenols and the related enzymes. In this respect, a method was developed to detect phenylalanine ammonia-lyase (PAL) activity in peach fruit.

Effects of Herbicides on Growth and Extractable Phenylalanine Ammonia-Lyase Activity in Light- and Dark-Grown Soybean (Glycine max) Seedlings

Weed Science ◽  
1981 ◽  
Vol 29 (4) ◽  
pp. 433-439 ◽  
Author(s):  
Robert E. Hoagland ◽  
Stephen O. Duke
Keyword(s):  
Glycine Max ◽  
Phenylalanine Ammonia Lyase ◽  
Dry Weight ◽  
Root Tip ◽  
Continuous Darkness ◽  
Soybean Seedlings ◽  
Pal Activity ◽  
Lyase Activity ◽  
Phenylalanine Ammonia Lyase Activity

Effects of 16 herbicides representing 14 herbicide classes on growth and extractable phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) were examined in light- and dark-grown soybean [Glycine max(L.) Merr. ‘Hill’] seedlings. High purity (96 to 100%) herbicides were supplied via aqueous culture at various concentrations: 0.5 mM amitrole (3-amino-s-triazole), 0.1 mM atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], 0.07 mM diclofop-methyl {methyl ester of 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoicacid}, 0.5 mM DSMA (disodium methanearsonate), 0.2 mM fenuron (1,1-dimethyl-3-phenylurea), 0.05 mM fluridone {1-methyl-3-phenyl-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone}, 0.5 mM MH (1,2-dihydro-3,6-pyridazinedione), 0.5 mM metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one], 1.8 μM nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline], 0.5 mM norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone], 0.05 mM paraquat (1,1′-dimethyl-4,4′-bipyridinium ion), 0.15 mM perfluidone {1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl] methanesulfonamide}, 0.2 mM propanil (3′,4′-dichloropropionanilide), 0.1 mM propham (isopropyl carbanilate), 0.5 mM TCA (trichloroacetic acid), and 0.05 mM 2,4-D [(2,4-dichlorophenoxy)acetic acid]. Dark-grown soybean seedlings (3-day-old) were transferred to control solutions (2 mM CaSO4) or to herbicide solutions (in 2 mM CaSO4) and grown at 25 C in continuous white light (200 μE•m-2•s-1) or continuous darkness until harvested 24 or 48 h after transfer. After 48 h, growth (fresh weight, dry weight, elongation) was inhibited by most of the chemicals. Other signs of toxicity (necrosis, secondary root stunting, and root tip swelling) were noted for some treatments. Roots were most affected, although hypocotyls were generally not changed. Hypocotyl elongation was stimulated by atrazine, fluridone, and norflurazon after 48 h light. Extractable PAL activity from soybean axes was decreased by atrazine, fenuron, metribuzin, norflurazon, propanil, propham, and 2,4-D. Amitrole and paraquat were the only herbicides that increased extractable PAL activity. Other compounds tested had no effect on the enzyme. None of the herbicides significantly affected in vitro PAL activity.

Acifluorfen Action on Growth and Phenolic Metabolism in Soybean (Glycine max) Seedlings

Weed Science ◽  
1989 ◽  
Vol 37 (6) ◽  
pp. 743-747 ◽  
Author(s):  
Robert E. Hoagland
Keyword(s):  
Glycine Max ◽  
Chlorophyll A ◽  
Root Elongation ◽  
Liquid Culture ◽  
Phenylalanine Ammonia Lyase ◽  
Hypocotyl Length ◽  
Phenolic Metabolism ◽  
Soybean Seedlings ◽  
Pal Activity ◽  
Chlorophyll Accumulation

Three-day-old soybean seedlings were treated with acifluorfen via liquid culture [50 μM in dark, 1 μM in light (200 μE·m–2·s–1)]. Root elongation in the dark was inhibited only slightly (6%) after 96 h. In the light, acifluorfen inhibited root elongation after 48 h; after 96 h, inhibition was 32%. Hypocotyl length was not affected in either the light or dark. Soluble hydroxyphenolic content per axis was unaffected in the dark but was reduced by about 13 to 25% at 24 to 96 h in the light. Extractable phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity per axis was unaltered by herbicide in the dark. A brief transient increase in PAL activity (4 to 24 h) in axes of light-grown seedlings in the presence of acifluorfen was followed by reduced enzyme levels compared to light-grown controls at 72 and 96 h. Although light is required for maximal herbicide action, there was no effect on anthocyanin or chlorophyll accumulation or on the chlorophyll a/b ratio in hypocotyls or light-grown seedlings.

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