The NAD-dependent and NADP-dependent alcohol dehydrogenase activities of strawberries (Fragaria xananassa Duch.) were found to have broad substrate specificities including those alcohols and aldehydes responsible for strawberry aroma and flavor either directly or through their ester products. NAD-dependent activities were greatest against short-chained alcohols, whereas the NADP-dependent activities were most active against aromatic and terpene alcohols. Differences were seen in substrate specificity between receptacle and achene alcohol dehydrogenase activities. Alcohol dehydrogenase activities were found to be developmentally regulated in receptacle tissue and increased during the period of fruit maturation and ripening. Isoelectric focusing of NAD-dependent ADH activities showed that several isozymes of this enzyme exist, that they differ between receptacle and achene tissues, and that they vary among specific genotypes. Our results suggest that NAD- and NADP-dependent ADH activities are integral components of flavor and fragrance volatile production in ripening strawberries.
William C. Mitchell and Gojko Jelenkovic
Ann M. Callahan and Carole L. Bassett
NADP-dependent Malic Enzyme (NADP-ME, EC 188.8.131.52) catalyzes the decarboxylation of malate, resulting in the release of CO2. In C3 plants the enzyme does not contribute CO2 directly to photosynthesis. Rather, it is associated with the supplemental synthesis of glycolytic and Krebs Cycle intermediates, although it may also be involved in regulating intracellular pH. NADP-ME activity increases during ripening of several fruits e.g. tomato and apple, usually in association with increased respiration of the developing fruit. We examined expression of NADP-ME during ripening in peach using a cDNA probe derived from F. trinervia (C4 dicot). The probe hybridized to a single RNA species of the predicted size and was low in abundance as expected for a C3 NADP-ME. As fruit matured, the RNA levels increased to a maximum around 133-140 days after bloom (fully ripe). NADP-ME RNA was not detectable from leaves isolated at the same time.
Michael Knee and Fernando L. Finger
Tomato (Lycopersicon esculentum Mill., cv. Ohio 7814) fruits were harvested weekly following flowering to relate changes in NADP+-malic enzyme (NADP-ME) activity and major organic acids (malate and citrate) to fruit development. Specific activity of NADP-ME and fresh weight concentrations of the acids reached maximal levels at the mature-green stage. During ripening, a decline in malate concentration was followed by decreases in NADP-ME activity and citrate concentration. Activity of NADP-ME and organic acid concentrations were highest in the locular gel, but activity also occurred in tomato leaves, stems, and roots. The data do not exclude a role for NADP-ME in the metabolism of organic acids during fruit ripening. However, it is also possible that the enzyme is involved in cytoplasmic pH regulation.
William C. Mitchell and Gojko Jelenkovic
Assays of enzyme activity, in vivo inhibition studies and the developmental analysis of strawberry (Fragaria × ananassa Duch.) fruit alcohol dehydrogenases (ADH) suggest that both the NAD-(E.C. 184.108.40.206) and the NADP-dependent (E.C. 220.127.116.11) forms of ADH enzymes play integral roles in the development and ripening of fruits. One role of ADH enzymes appears to be the evocation of changes in sugar, soluble solids, acidity and volatile compounds necessary for the normal organoleptic character of strawberry fruits. The data presented includes: 1.) The wide substrate specificity of both ADH enzymes for the “fragrance and flavor alcohols and aldehydes” synthesized by ripe strawberry fruits, 2.) the effect of inhibitors of ADH activity upon strawberry fruit ripening, and 3.) the comparative regulation of NAD- and NADP-ADH enzymes including 4.) the developmental control of ADH enzymes in strawberry fruits.
Manuela Zude-Sasse, Ulrich Hartmond, Georg Ebert, and Peter Lüdders
Soil flooding reduces partial pressure of oxygen (pO2) in the root zone and often results in a reduction in photosynthesis and growth. In greenhouse studies, rooted stem cuttings of the mango (Mangifera indica L.) rootstock selection 13/1 were exposed to anoxia by saturating the root zone with N2 for up to 52 h. Reduced pO2 in the root zone affected the energy status of the roots and particularly enhanced the phosphorylated and nonphosphorylated pyridine nucleotide charges—the ratio of reduced Nicotinamide-adenine-dinucleotides [NAD(P)H] to total Nicotinamide-adenine-dinucleotide content [oxidized NAD(P)+ plus NAD(P)H]—that drive the redox reaction rates in cell metabolism. Also, the pyridine nucleotide charges in leaves were enhanced, while the photosynthetic rate decreased following reduction in pO2 in the root zone. During up to 4 h of reduced pO2, the ratio of internal CO2 concentration in the mesophyll to ambient CO2 concentration was unchanged. This implies a nonstomatal influence on photosynthesis. In addition, light saturation of photosystem II occurred at lower irradiance (470 μmol·m-2·s-1) resulting in reduced maximum photochemical efficiency below that of the high pO2 controls. After 28 h of reduced pO2, NAD(P) charges in the leaves returned to normal, diminishing its potential effect on net photosynthetic rate.
Suping Zhou, Roger J. Sauvé, Zong Liu, Sasikiran Reddy, Sarabjit Bhatti, Simon D. Hucko, Yang Yong, Tara Fish, and Theodore W. Thannhauser
, ferredoxin-NADP (+) reductase in the electron transport chain of PSI (spot 1710: –2.1-fold expression), Rubisco (Ribulose 1, 5-bisphosphate carboxylase/oxygenase) activase (spots 1745 and 1013: –2.1- and –1.5-fold, respectively), and transketolase (spot 130
Dongfeng Liu, Junbei Ni, Ruiyuan Wu, and Yuanwen Teng
/v), polyvinylpolypyrrolidone (1%, w/v), and 2-mercaptoethanol (20 m m ), and the activities of S6PDH (reduction of G6P activity), NAD + -SDH, and NADP + -SDH were assayed by measuring the absorbance of nicotinamide adenine dinucleotide phosphate (NADPH) or nicotinamide adenine
Brandon R. Smith and Lailiang Cheng
MgSO 4 , 5 m m MnCl 2 , 1 m m DTT, 0.5 m m NADP, 2 units of NADP-isocitrate dehydrogenase (IDH), and 75 μL of enzyme extract. The reaction was initiated by adding 10 m m cis -aconitate. NAD-malic enzyme was assayed by measuring the amount of
Suping Zhou, Roger Sauve, Tara Fish, and Theodore W. Thannhauser
protein, ferredoxin-NADP (+) reductase and quinone oxidoreductase-like protein, and the reduction of rubisco activase ( Table 2 ). The expressed sequence tags (ESTs) for other proteins were not found on microarray chips; consequently, their transcriptional
Zehuang Zhang, Qihua Lin, and Qiuzhen Zhong
: 0006355), pollen exine formation (GO: 0010584), sporopollenin biosynthetic process (GO: 0080110), plasma membrane (GO: 0005886), sequence-specific DNA binding transcription factor activity (GO: 0003700), and 2-alkenal reductase [NAD(P)] activity (GO