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Dipayan Sarkar, Prasanta C. Bhowmik, Young-In-Kwon and Kalidas Shetty

showed the highest basal SDH activity in nonacclimated conditions. The lowest SDH activity was observed in acclimated perennial ryegrass plants. Fig. 2. Glucose-6-phosphate dehydrogenase (G6PDH) ( A ) and succinate dehydrogenase (SDH) ( B ) of

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Shiow Y. Wang, Hong J. Jiao and Miklos Faust

The activity of glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphate gluconate dehydrogenase (6PGDH), isocitrate dehydrogenase (ICDH), pyruvate kinase (PK), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were studied in apple (Malus domestics Borkh.) buds during dormancy and thidiazuron-induced budbreak. When buds were dormant, the activity of the glycolytic enzymes GAPDH and PK and the tricarboxylic acid (TCA) cycle enzyme ICDH was low compared to that in nondormant buds. The activity of these enzymes increased during budbreak, peaked when buds were in the green tip stage just before the start of rapid expansion (at 8 days after thidiazuron treatment), and declined thereafter. The activity of pentose-phosphate cycle enzymes G6PDH and 6PGDH was higher in dormant buds than in nondormant buds. 6PGDH was about twice as high as G6PDH. During budbreak and resumption of growth, G6PDH and 6PGDH activity decreased.

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Hening Hu and Gary A. Couvillon

The activities of catalase and of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH), the two key enzymes in the pentose phosphate pathway (ppp), were measured in the seeds of Prunus persica (L.) Batsch var. nectarina Maxim `Nectarine 7'. The seeds were subjected to three imbibition treatments: 1) continuous 24C; 2) continuous 4C; and 3) application of thiourea (TU)/gibberellic acid (GA) at various concentrations to seed held at 24C then subsequently chilled at 4C. Treatments of continuous 24 or 4C indicated that catalase, G6PDH, and 6PGDH exhibited significant activity increases only when the seeds obtained germination potential, which occurred in the seeds chilled for 7 weeks at 4C. Seeds held at 24C did not germinate and showed little change with time in G6PDH and 6PGDH activity. There was only a slight increase in catalase activity beginning 3 weeks following treatment initiation and a decrease in activity following 13 weeks of treatment. Thiourea treatment resulted in an inhibition of catalase activity and a stimulation of G6PDH, but had no effect on 6PGDH activity. However, no correlation between enzymic activity and seed germination was found. The results strongly questioned the role of the ppp and catalase activity in dormancy control as previously hypothesized.

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Brandon R. Smith and Lailiang Cheng

. NADP-malic enzyme, glucose-6-phosphate dehydrogenase (G6PDH), and NAD(P)-IDH were assayed according to Passonneau and Lowry (1993) with some modifications. NADP-malic enzyme activity was measured in a 1-mL mixture containing 100 m m Bicine-KOH pH 8

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Y.H. Huang, David H. Picha and Charles E. Johnson

The glucose-6-phosphate dehydrogenase (G-6-PDH) and glucose oxidase methods are commonly adapted for plant invertase assay. A disadvantage of the G-6-PDH assay is the relatively high cost of the coupling enzymes and cofactors. A disadvantage of the glucose oxidase method, which uses a glucose kit (Sigma, 510-A), is the presence of high activities of acid invertase and alkaline invertase in the PGO enzyme formula (peroxidase and glucose oxidase), which gives a falsely high invertase activity value. An alternative and inexpensive coupled assay was developed for enzymatic assay of plant invertases. In this assay, ADP produced from phosphorylation of glucose and fructose (hydrolysis products of invertases) is coupled to oxidation of NADH by the enzymes pyruvate kinase and lactate dehydrogenase in presence of phosphoenolpyruvate and NADH. This method was compared with the glucose-6-phosphate dehydrogenase method by using protein preparations derived from plant materials of three different species. Statistical analysis indicated that the alternative assay was similar in accuracy to the glucose-6-phosphate dehydrogenase method, with an advantage of reducing the cost from $0.85 to $0.35 per assay.

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Candice A. Shoemaker and Michael Barnett

Viburnum bracteatum Rehd. is a member of the “dentatum” complex represented by at least three types: V. bracteatum, V. dentatum L., and V. rafinesquianum Schult. V. bracteatum is an endangered species in Georgia and at the federal level is a candidate as an endangered species. Two populations were located in northwestern Georgia; however, there is some concern as to whether they are in fact V. bracteatum. To determine if it is possible to distinguish between the three Viburnum species, cellulose acetate electrophoresis to detect isozyme variation was done. Polymorphic enzymes resolved were alcohol dehydrogenase, malic dehydrogenase, glucose-6-phosphate dehydrogenase, malic enzyme, 6-phosphogluconate dehydrogenase, phosphoglucomutase, and phosphoglucose isomerase. Fresh bud tissue was used, and tissue samples were electrophoresed three times for each enzyme assayed. A review of 100 phylogeny trees created with Dollop analysis was done. V. rafinesquianum, the known sample of V. bracteatum, and the 12 samples of possible V. bracteatum were all equally parsimonious. V. dentatum was consistently an outgroup. In conclusion, isozyme variation can assist in Viburnum species distinction.

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Lisa Tang, Shweta Chhajed, Tripti Vashisth, Mercy A. Olmstead, James W. Olmstead and Thomas A. Colquhoun

). Interestingly, DEGs encoding enzymes in the PPP, such as glucose-6-phosphate dehydrogenase [ G6PD (Prupe.6G307600)] and transketolase (Prupe.2G143600), were upregulated at 3 DAT, indicating an increase in NADPH in the buds of trees treated with HC. At 7 DAT

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Yong Zhang, Chunxia Fu, Yujing Yan, Xiaodan Fan, Yan’an Wang and Ming Li

.5 mL of the solution was withdrawn and boiled. After adding 1 mL of 0.1 M Tris-HCl buffer (pH 8.0), the glucose produced was analyzed enzymatically using yeast hexokinase (Sigma), grade-I yeast glucose-6-phosphate dehydrogenase (Sigma), adenosine-5

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Yuanyuan Miao, Qiaosheng Guo, Zaibiao Zhu, Xiaohua Yang, Changlin Wang, Yuan Sun and Li Liu

.4 unit phosphoglucomutase and 10 µL 0.4 unit glucose-6-phosphate dehydrogenase were added to the reaction solution and mixed, and the increase in absorbance at 340 nm in 2 min was recorded. One unit of AGPase was defined as the quantity of enzyme needed

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Rebecca L. Darnell, Nicacio Cruz-Huerta and Jeffrey G. Williamson

/μL) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49, 0.08 units/μL) to measure glucose; 2) “ESB”—“ESA” and phosphogalactoisomerase (EC 5.3.1.9, 0.07 units/μL) to measure glucose and fructose; and 3) “ESC”—“ESB” and invertase (EC 3.2.1.26, 0.80 units