scholarly journals Biosynthesis of α-Farnesene in Apple Fruit

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 458A-458
Author(s):  
H.P.V. Rupasinghe ◽  
G. Paliyath ◽  
D.P. Murr
Keyword(s):  
Enzyme Purification ◽  
Apple Fruit ◽  
Oxidation Products ◽  
Purification And Characterization ◽  
Developing Regions ◽  
Physiological Disorder ◽  
Superficial Scald ◽  
Feeding Experiments ◽  
Surface Wax

α-Farnesene is an acyclic sesquiterpene hydrocarbon that is a constituent of the surface wax of apples (Malus domestica Borkh.). Although, oxidation products of α-farnesene have been implicated in the development of the physiological disorder superficial scald in apple, the mechanism of α-farnesene biosynthesis has not been studied in detail. We are currently investigating α-farnesene biosynthesis in relation to superficial scald development in apples. Radiolabelled feeding experiments using isolated tissue segments indicated that α-farnesene is derived from trans,trans-farnesyl pyrophosphate (FPP), mainly in the skin rather than cortex. Among the other labeled products detected, farnesol level was over a hundred-fold higher compared to α-farnesene. However, [1-3H] trans,trans-Farnesol was not incorporated into α-farnesene. Feeding radiolabelled FPP to skin tissue segments of scald-developing and normal apples showed differential incorporation of radiolabel into various products. Though the incorporation into α-farnesene was nearly the same, there was higher levels of incorporation into farnesyl esters in normal apples. As well, the levels of radiolabelled in the farnesol fraction was three times higher in scald-developing regions. These results indicate that there are potential difference in the biosynthesis and metabolism of farnesyl components between scald-developing and normal apples. In studies using cell-free extracts, farnesol formation was observed from labeled FPP and was two-fold higher in crude membrane extract compared to crude cytosol. Our results indicate that α-farnesene formation in apple fruit tissue is through FPP and is possibly catalyzed by a single sesquiterpene synthase enzyme. Purification and characterization of this enzyme are in progress.

scholarly journals Intermittent Warming Effects on Superficial Scald of Apple Fruit

HortScience ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 605b-605
Author(s):  
Thair F. Alwan ◽  
Christopher B. Watkins
Keyword(s):  
Fruit Ripening ◽  
Marked Reduction ◽  
Apple Fruit ◽  
Oxidation Products ◽  
Superficial Scald ◽  
Cooperative Agreement ◽  
Postharvest Treatments ◽  
Conjugated Trienes ◽  
Hexane Extracts ◽  
Intermittent Warming

Fruit of `Cortland', `Delicious' and `Law Rome' were warmed for 24 hours at 20°C either weekly, once every 2 weeks, or once every 3 weeks during storage. The effect of these treatments on fruit ripening and concentrations of alpha-farnesene and conjugated trienes in hexane extracts of the skin were measured during storage. Without warming, scald incidence of the cultivars was 70%, 14%, and 85%, respectively. Intermittent warming treatments resulted in a marked reduction of scald though effectiveness was affected by cultivar. In `Cortland', scald was reduced only by the weekly warming treatment (10%) as was less effective than DPA (1%). In `Delicious', all warming treatments were equally effective. In `Law Rome', weekly warming resulted in better control of scald (3%) than DPA (14%) and less frequent warming was proportionately less effective in controlling the disorder. Concentrations of conjugated trienes at 281 nm did not relate consistently to scald incidence after storage. However, ratios of conjugated trienes of 258 nm or 269 nm with 281 nm strongly support a hypothesis that non-toxic and toxic oxidation products of alpha-farnesene interact and influence the effectiveness of postharvest treatments on scald control (Du and Bramlage, 1993; JASHS 118:807-813). A hypothesis relating the interactions between ripening and scald development will be presented. Supported in part by USDA Specific Cooperative Agreement 58-1931-5-017.

scholarly journals Expression of Alpha-farnesene Synthase Gene AFS1 in Relation to Levels of Farnesene and Conjugated Trienols in Peel Tissue of Scald-susceptible `Law Rome' and Scald-resistant `Idared' Apple fruit

HortScience ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 782B-782
Author(s):  
Steven W. Pechous ◽  
Bruce D. Whitaker* ◽  
Christopher B. Watkins
Keyword(s):  
Sharp Increase ◽  
Biosynthetic Pathway ◽  
Apple Fruit ◽  
Oxidation Products ◽  
High Rate ◽  
Subsequent Increase ◽  
Transcript Levels ◽  
Superficial Scald ◽  
Apple Peel ◽  
Apple Cultivars

Fruit of different apple cultivars vary widely in susceptibility to superficial scald. The genetic and biochemical factors involved in this variation are unknown. Conjugated trienol (CTol) oxidation products of alpha-farnesene have been linked with scald induction, and a high rate of farnesene synthesis in peel tissue of scald-prone apples early in storage is often associated with development of the disorder. Pre-storage treatment of apple fruit with 1-methylcyclopropene (1-MCP) inhibits the early burst of farnesene production and prevents scald, suggesting that ethylene induces transcription of genes involved in farnesene synthesis. We recently cloned a gene from apple peel tissue, AFS1, which encodes alpha-farnesene synthase, the last enzyme in the farnesene biosynthetic pathway. In this study, expression of AFS1 was compared in scaldsusceptible Law Rome (LR) and scald-resistant Idared (IR) apples at harvest and over 20 weeks of storage at 0.5 C. AFS1 transcript levels were closely correlated with accumulation of farnesene and CTols. In fruit of both cultivars, a sharp increase in AFS1 mRNA during the first 4 to 8 weeks of storage preceded a proportional rise in farnesene and a subsequent increase in CTols. However, maximum levels of AFS1 transcript, farnesene, and CTols were, respectively, 2.5-, 4-, and 33-fold greater in LR than in IR apples. Treatment of fruit with 1-MCP at harvest suppressed the increases in AFS1 transcript and farnesene early in storage, but AFS1 expression and farnesene synthesis recovered in LR fruit after 20 weeks. Scald incidence in LR apples after 20 weeks at 0.5 °C plus 1 week at 20 °C averaged 86%, whereas IR fruit had no scald. 1-MCP treatment reduced scald incidence in LR to <1%.

Purification and characterization of a thermostable glucoamylase fromAspergillus fumigatus

1998 ◽  
Vol 44 (5) ◽  
pp. 493-497 ◽  
Author(s):  
William Brandani da Silva ◽  
Rosane Marina Peralta
Keyword(s):  
Aspergillus Fumigatus ◽  
Molecular Mass ◽  
Enzyme Purification ◽  
Soluble Starch ◽  
Carbohydrate Content ◽  
Apparent Molecular Mass ◽  
Starch Hydrolysis ◽  
Purification And Characterization ◽  
Original Activity

A thermostable glucoamylase from Aspergillus fumigatus was purified to homogeneity. It was a glycoprotein with 23% carbohydrate content and an apparent molecular mass of 42 kDa. The enzyme showed maximal activities at pH 4.5-5.5 and 65°C and preferentially attacked polysacharides, such as starch, glycogen, amylopectin, and amylose, rather than maltose and maltoriose. The Kmand Vmaxof soluble starch hydrolysis at 40°C and pH 5.0 were 0.1 mg ·mL-1and 161 µmol glucose equivalents liberated ·min-1·mg protein-1, respectively. The purified enzyme was remarkably insensitive to glucose. It was not affected by 500 mM D-glucose and retained about 80% of its original activity in the presence of 1000 mM of this sugar.Key words: amylase, Aspergillus fumigatus, enzyme purification, glucose insensitive, thermostableglucoamylase.

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