Hydroperoxy-arachidonic acid mediated n-hexanal and (Z)-3- and (E)-2-nonenal formation in Laminaria angustata

In higher plants, C6 and C9 aldehydes are formed from C18 fatty acids, such as linoleic or linolenic acid, through formation of 13- and 9-hydroperoxides, followed by their stereospecific cleavage by fatty acid hydroperoxide lyases (HPL). Some marine algae can also form C6 and C9 aldehydes, but their precise biosynthetic pathway has not been elucidated fully. In this study, we show that Laminaria angustata, a brown alga, formed C6 and C9 aldehydes enzymatically. The alga forms C9 aldehydes exclusively from the C20 fatty acid, arachidonic acid, while C6 aldehydes are derived either from C18 or from C20 fatty acid. The intermediates in the biosynthetic pathway were trapped by using a glutathione/glutathione peroxidase system, and subjected to structural analyses. Formation of (S)-12-, and (S)-15-hydroperoxy arachidonic acids [12(S)HPETE and 15(S)HPETE] from arachidonic acid was confirmed by chiral HPLC analyses. These account respectively for C9 aldehyde and C6 aldehyde formation, respectively. The HPL that catalyzes formation of C9 aldehydes from 12(S)HPETE seems highly specific for hydroperoxides of C20 fatty acids.     

Biomimetic conversion of (3S)-(-)-neodictyoprolenol to optically pure (1S,2R)-(-)-dictyopterene B,marine algal sex pheromone

Both enantiomers of (3S)-(-)- and (3R)-(+)-Neodictyoprolenol [(3S,5Z,8Z)-(-)-1,5,8-undecatrien-3-ol] were successfully converted to the algal sex pheromone, (1S,2R)-(-)-dictyopterene B and (1R,2S)-(+)-dictyopterene B in high enantiomeric purities (e. e. > 99%), respectively, by the biomimetic reaction involving phosphorylation and elimination under a mild condition.     

2,4-Decadienals are produced via (R)-11-HPITE from arachidonic acid in marine green alga Ulva conglobata

Marine green alga Ulva conglobata was investigated for the biogeneration of oxygenated products from exogenously added arachidonic acid (ARA). A crude enzyme from the alga afforded the detectable amount of a hydroperoxyicosatetraenoic acid (HPITE), which was identified as (R)-11-HPITE by HPLC and GC-MS. Headspace-SPME method indicated that ARA was selectively used to form 2,4-decadienals. These results showed that 2,4-decadienals are produced via (R)-11-HPITE from ARA exclusively.     

Structure-activity relationships of seco-prezizaane terpenoids in gamma-aminobutyric acid receptors of houseflies and rats

Thirteen seco-prezizaane terpenoids isolated from star anise species (Illcium floridanum, Illcium parviflorum, and Illcium verum) were investigated for their ability to inhibit the specific binding of [(3)H]4'-ethynyl-4-n-propylbicycloorthobenzoate (EBOB), a non-competitive antagonist of gamma-aminobutyric acid (GABA) receptors, to housefly-head and rat-brain membranes. Veranisatin A was found to be the most potent inhibitor in both membranes, with an IC(50)(fly) of 78.5 nM and an IC(50)(rat) of 271 nM, followed by anisatin (IC(50)(fly)=123 nM; IC(50)(rat)=282 nM). Six of the other 11 tested compounds were effective only in housefly-head membranes. Pseudoanisatin proved to display a high (>26-fold) selectivity for housefly versus rat GABA receptors (IC(50)(fly)=376 nM; IC(50)(rat) >10,000 nM). Although pseudoanisatin does not structurally resemble EBOB, Scatchard plots indicated that the two compounds bind to the same site in housefly receptors. Anisatin and pseudoanisatin exhibited moderate insecticidal activity against German cockroaches. Comparative molecular field analysis (CoMFA), a method of three-dimensional quantitative structure-activity relationship (3D-QSAR) analysis, demonstrated that seco-prezizaane terpenoids can bind to the same site as do picrotoxane terpenoids such as picrotoxinin and picrodendrins, and the CoMFA maps allowed us to identify the parts of the molecules essential to high activity in housefly GABA receptors.     

Gas Exchange Characteristics in Rice Leaves Grown under the Conditions of Physiologically Low Temperature and Irradiance

The photosynthetic rate measured at 20°C was higher in ricegrown under 20/18°C day/night temperature and 350 µmoIquanta m^–2s^–1 than in rice grown under 25/20°Cand 1,000 µmol quanta m^–2s^–1, whereas therewas no difference in the photosynthetic rate measured at 25°Cbetween rice grown in these two ways. This difference was suggestedto be caused by an enhanced ribulose-l,5-bis-phosphate-regenerationcapacity in the low-temperature/ir-radiance-grown rice. (Received July 14, 1998; Accepted September 25, 1998)     

Light-dependent fragmentation of the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase in chloroplasts isolated from wheat leaves

The large subunit (LSU) of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) is degraded into an N-terminal side fragment of 37 kDa and a C-terminal side fragment of 16 kDa by the hydroxyl radical in the lysates of chloroplasts in light (H. Ishida et al. 1997, Plant Cell Physiol 38: 471–479). In the present study, we demonstrate that this fragmentation of the LSU also occurs in the same manner in intact chloroplasts, and discuss the mechanisms of the fragmentation. The fragmentation of the LSU was observed when intact chloroplasts from wheat leaves were incubated under illumination in the presence of KCN or NaN₃, which is a potent inhibitor of active oxygen-scavenging enzyme(s). The properties, such as molecular masses and cross-reactivities against the site-specific anti-LSU antibodies, of the fragments found in the chloroplasts were the same as those found in the lysates. These results indicate that, as in the lysates, the fragmentation of the LSU in the intact chloroplasts was also caused by the hydroxyl radical generated in light. The fragmentation of the LSU was completely inhibited by 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU), and only partially inhibited by methyl viologen in the lysates. The addition of hydrogen peroxide to the lysates stimulated LSU fragmentation in light, but did not induce any fragmentation in darkness. Thus, we conclude that both production of hydrogen peroxide and generation of the reducing power at thylakoid membranes in light are essential requirements for fragmentation of the LSU. Received: 14 June 1997 / Accepted: 28 August 1997     

Fatty acid hydroperoxide lyase in tobacco cells cultured in vitro

Fatty acid hydroperoxide lyase (HPO lyase) was found in green and non-green tobacco cells cultured in vitro. The HPO lyase activity in non-green cells was $\text{1}\text{3}$-$\text{1}\text{2}$ of that in green cells. When the cells were transferred from the light to dark conditions or vice versa, cells turned non-green or green according to the light conditions. The HPO lyase activity also changed according to the light conditions, but the changes in HPO lyase activities were not proportional to the changes in chlorophyll contents. These results suggest that at least two types of HPO lyases are present in the green cells. One type of HPO lyase is perhaps common both to the green and non-green cells; another one is chloroplastic. The fatty acid compositions of cells and substrate specificities of HPO lyase differed between green and non-green cells.     

A gerontological cohort study of aged twins: the Osaka University Aged Twin Registry.

We describe subject recruitment and research results from the Osaka University Aged Twin Registry (OUATR). The research focus of OUATR is the genetic and environmental contributions to physical-cognitive-mental aging which we examined in Japanese twins in later adulthood. Within this large-scale registry (12,000 pairs) of oriental twins born between 1900 and 1935, approximately 10% of participants are MZ twins reared apart from early childhood. Two hundred and fifty pairs have had comprehensive medical examinations, including various blood chemical panels, lymphocyte subtests, WAIS (Wechsler Adult Intelligence Scale), and urine analysis. The future foci of this study are primarily on longevity, decline of cognitive functions with aging, bio-physiological functions, lifestyle and behavior genetics, and psycho-spiritual functions.     

Cellular localization of NADH-dependent glutamate-synthase protein in vascular bundles of unexpanded leaf blades and young grains of rice plants

Tissue and cellular localization of NADH-dependent glutamate synthase (NADH-GOGAT, EC 1.4.1.14) in the unexpanced leaf blades and young grains of rice (Oryza sativa L.) was investigated using tissue-print immunoblot and immunocytological methods with an affinity-purified anti-NADH-GOGAT immunoglobulin G. Tissue-print immunoblots showed that the NADH-GOGAT protein was mostly located in large and small vascular bundles of the unexpanded blades. When the cross-sections (10μ in thickness) prepared from the paraffin-embedded blades were stained with the antibody, the NADH-GOGAT protein was detected in vascular-parenchyma cells and mestome-sheath cells. In developing grains, the NADH-GOGAT protein was detected in both phloem- and xylem-parenchyma cells of dorsal and lateral vascular bundles, and in the nucellar projection, nucellar epidermis, and aleurone cells. On the other hand, ferredoxin (Fd)-dependent GOGAT (EC 1.4.7.1) was located mainly in mesophyll cells of the leaf blade and in chloroplast-containing cross-cells of the pericarp of the grains. The spatial expression of these GOGAT proteins indicates distinct and non-overlapping roles in rice plants. In the leaf blades and young grains, NADH-GOGAT could be involved in the synthesis of glutamate from the glutamine that is transported through the vascular system from roots and senescing tissues.     

Fractionation of Nitrogen Isotopes by Glutamine Synthetase Isolated from Spinach Leaves

The isotopic fractionation of nitrogen in the reaction in vitroof glutamine synthetase isolated from spinach (Spinacia oleraceaL.) leaves was calculated from the changes in natural ¹⁵N abundance(