外源精胺、亚精胺作用下离体小麦叶片老化过程中蛋白水解酶活性和内源精胺、亚精胺含量的变化(简报)

外源精胺、亚精胺明显抑制离体小麦叶片老化过程中蛋白水解酶活性上升 ;小麦叶片老化期间内源精胺、亚精胺含量逐渐下降 ,与蛋白水解酶活性升高对应     

精胺与亚精胺对光照下玉米离体叶片光合羧化酶活性的影响（简报）

玉米离体叶片在光下衰老时,其RuBPC、PEPCase和PPDK（丙酮酸磷酸二激酶）活性逐渐降低。精胺（Spm）和亚精胺（Spd）可阻止这三种酶的活性下降,还可阻止叶绿素和可溶性蛋白含量下降,延缓光下玉米离体叶片的衰老。     

外源精胺对水分胁迫下小麦幼苗保护酶活性的影响

通过营养液培养试验,研究了水分胁迫下外源精胺(Spm)对抗旱性不同的小麦品种幼苗叶片质膜相对透性及保护酶活性的影响.结果表明:水分胁迫下,小麦叶片的质膜相对透性、M DA含量增加、SOD、CAT和POD活性上升,外源精胺处理可延缓水分胁迫下小麦叶片质膜相对透性和M DA含量上升,提高了SOD、CAT、POD酶活性的上升幅度;并且对抗旱性弱的品种保护酶活性增幅高于抗旱性强的品种.因此,外源精胺处理对抗旱性弱的品种缓解水分胁迫作用大于抗旱性强的品种.     

精胺和亚精胺影响水稻种子萌发与温度的关系(简报)

在25℃下以0．01～1．0mmol·L-1精胺和0．01～0．1mmol·L-1亚精胺预处理水稻种子48h，可以提高16℃下萌发指数和活力指数，但对28℃下的种子萌发无影响。种子萌发时胚芽中α-淀粉酶活性和胚芽、胚根的呼吸速率的变化规律基本上与活力指数相似。     

外源亚精胺和精胺对NaHCO3胁迫下南蛇藤抗氧化系统的影响

研究了叶面喷施亚精胺和精胺对NaHCO₃胁迫下南蛇藤叶片抗氧化系统的影响.结果表明：外源亚精胺和精胺处理使NaHCO₃胁迫下南蛇藤叶片O₂^-·产生速率、H₂O₂、丙二醛(MDA)含量和电解质外渗率显著降低(P<0.05).亚精胺处理明显提高了盐胁迫下超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)和抗坏血酸过氧化物酶(APX)等抗氧化酶的活性,以及还原型谷胱甘肽(GSH)、类胡萝卜素(CAR)和脯氨酸(Pro)等抗氧化剂的含量,但对还原型抗坏血酸(AsA)含量没有作用;精胺处理明显提高NaHCO₃胁迫下POD和APX的活性以及GSH、CAR和Pro的含量,但对SOD和AsA含量影响不显著,甚至引起CAT活性明显降低.亚精胺和精胺处理明显改善了NaHCO₃胁迫下南蛇藤的生长.外源亚精胺和精胺可以改善NaHCO₃胁迫下南蛇藤叶片的膜保护功能,减少叶片中活性氧的积累,从而提高南蛇藤对NaHCO₃胁迫的抗性.     

外源精胺对小麦幼苗抗氧化酶活性的促进作用

外源精胺（Spm)降低了离体小麦叶片衰老时MDA的含量,且降低程度与精胺的浓度成正比,0.2mmol/L的精胺提高了小麦幼苗体内的超氧化物歧化酶（SOD）,过氧化氢酶（CAT）,过氧化物酶（POD）及抗坏血酸过氧化物酶（ASP）的活性,体内及体外试验表明：精胺既可诱导SOD与POD的合成,又可直接作用于酶分子上以提高酶的活性;精胺对CAT合成仅能诱导,对已有酶活性无调节作用;精胺对ASP的合成无影响,却能促进已有酶的活性。     

干旱胁迫与小麦幼苗亚精胺代谢变化的关系

通过对亚精胺（spermidine,Spd）在抗旱性不同的小麦品种幼苗中的作用的研究,发现抗旱品种周麦18号在渗透胁迫处理时,其叶片中的Spd含量明显大于不抗旱的豫麦51号。用Spd合成的抑制剂甲基乙二醛-双（鸟嘌呤腙MGBG）处理周麦18号,则导致Spd含量下降和抗性的降低,外源Spd又可逆转MGBG对周麦18号在渗透胁迫下的伤害。外源Spd可以明显提高豫麦51号的叶片内Spd含量,并相应提高其抗性。以上结果表明,Spd可以提高小麦幼苗的抗渗透胁迫能力。     

外源精胺对小麦幼苗抗氧化酶活性的促进作用

外源精胺（Spm）降低了离体小麦叶片衰老时MDA的含量,且降低程度与精胺的浓度成正比。0.2mmol/L的精胺提高了小麦幼苗体内的超氧化物歧化酶（SOD）,过氧化氢酶（CAT）,过氧化物酶（POD）及抗坏血酸过氧化物酶（ASP）的活性。体内及体外试验表明精胺既可诱导SOD与POD的合成,又可直接作用于酶分子上以提高酶的活性;精胺对CAT合成仅能诱导,对已有酶活性无调节作用;精胺对ASP的合成无影响,却能促进已有酶的活性。     

亚精胺诱导自噬的作用机制

亚精胺(spermidine)是含有3个胺基的低分子量脂肪族碳化物,是存在于所有生物体中的天然多胺之一。自噬(autophagy)对于降解细胞内受损蛋白质和细胞器是必需的。外源性亚精胺可作为自噬的天然诱导剂,并且是安全和无毒的。新近研究表明,亚精胺可通过AKT/AMPK-FoxO3-Atg途径诱导自噬,还能促进组蛋白脱乙酰基酶4(histone deacetylase 4,HDAC4)向细胞核转运,降低细胞质HDAC4含量,进而增强微管相关蛋白1S(microtubule-associated protein 1S,MAP1S)乙酰化和稳定性以激活自噬。此外,亚精胺可作为乙酰转移酶抑制剂调节EP300活性,进而改变Atg5、Atg7、LC3和Atg12的乙酰化状态。同时,还可通过诱导哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)去磷酸化,激活ULK1/2-Atg13-FIP200复合物参与调控动物机体内的自噬过程。本文就自噬概念和亚精胺诱导自噬作用途径的最新研究进展作一综述。     

精胺和亚精胺对油菜几个生理指标的影响

油菜幼苗期和蕾苔期分别以不同浓度的精胺 (Spm)和亚精胺 (Spd)喷施后 ,幼苗期和蕾苔期的叶绿素含量、硝酸还原酶活性、可溶性糖含量、根系活力均提高 ,以 0 .0 1～ 1mmol·L-1浓度范围的效果最好。在相同浓度条件下 ,Spm的效果优于Spd ,蕾苔期处理的效果优于幼苗期     

C-Methylated Analogs of Spermine and Spermidine: Synthesis and Biological Activity

Russian Journal of Bioorganic Chemistry - Biogenic polyamines spermine and spermidine are present in eukaryotic cells in micro- and millimolar concentrations, that determines the multiplicity of...     

NaCl胁迫对白刺幼苗体内游离态亚精胺和精胺含量的影响

以西伯利亚白刺试管苗为材料,研究其在0、50和200 mmol·L-1NaCl胁迫及外源环己胺调控下,生物量和体内多胺含量的改变,以探讨多胺对盐生植物白刺在盐胁迫下的生理调节功能.结果显示:50 mmol·L-1NaCl更有利于西伯利亚白刺的生长,处理后30 d白刺根系和地上部干重分别比对照增加75%和95%,处理15 d生根率比对照提高44.42%.而0(对照)和200 mmol·L-1NaCl都显著抑制白刺试管苗的生根与生长;200 mmol·L-1NaCl处理45 d时地上部干重比对照显著降低11.71%.白刺叶片中的多胺(精胺和亚精胺)含量随着盐浓度的增加呈降低趋势,茎和根中的多胺含量在200 mmol·L-1NaCl处理后才显著受到抑制;同时施环己胺和200 mmol·L-1NaCl处理使白刺叶片中的亚精胺含量显著低于200 mmol·L-1NaCl处理组,且叶绿素合成减少,细胞质膜透性增高.研究表明,西伯利亚白刺叶片内保持合适的多胺含量可能是其适应盐渍环境的重要机制之一.     

Putrescine Aminopropyltransferase Is Responsible for Biosynthesis of Spermidine,Spermine, and Multiple Uncommon Polyamines in Osmotic Stress-Tolerant Alfalfa

The biosynthesis of polyamines from the diamine putrescine is not fully understood in higher plants. A putrescine aminopropyltransferase (PAPT) enzyme activity was characterized in alfalfa (Medicago sativa L.). This enzyme activity was highly specific for putrescine as the initial substrate and did not recognize another common diamine, 1,3-diaminopropane, or higher-molecular-weight polyamines such as spermidine and spermine as alternative initial substrates. The enzyme activity was inhibited by a general inhibitor of aminopropyltransferases, 5[prime]-methylthioadenosine, and by a specific inhibitor of PAPTs, cyclohexylammonium sulfate. The initial substrate specificity and inhibition characteristics of the enzyme activity suggested that it is a classical example of a PAPT. However, this enzyme activity yielded multiple polyamine products, which is uncharacteristic of PAPTs. The major reaction product of PAPT activity in alfalfa was spermidine. The next most abundant products of the enzyme reaction using putrescine as the initial substrate included the tetramines spermine and thermospermine. These two tetramines were distinguished by thin-layer chromatography to be distinct reaction products exhibiting differential rates of formation. In addition, the uncommon polyamines homocaldopentamine and homocaldohexamine were tentatively identified as minor enzymatic reaction products but only in extracts prepared from osmotic stresstolerant alfalfa cultivars. PAPT activity from alfalfa was highest in meristematic shoot tip and floral bud tissues and was not detected in older, nonmeristematic tissues. Product inhibition of the enzyme activity was observed after spermidine was added into the in vitro assay for alfalfa PAPT activity. A biosynthetic pathway is proposed that accounts for the characteristics of this PAPT activity and accommodates a novel scheme by which certain uncommon polyamines are produced in plants.     

Protective Action of Spermine and Spermidine against Photoinhibition of Photosystem I in Isolated Thylakoid Membranes

The photo-stability of photosystem I (PSI) is of high importance for the photosynthetic processes. For this reason, we studied the protective action of two biogenic polyamines (PAs) spermine (Spm) and spermidine (Spd) on PSI activity in isolated thylakoid membranes subjected to photoinhibition. Our results show that pre-loading thylakoid membranes with Spm and Spd reduced considerably the inhibition of O₂ uptake rates, P700 photooxidation and the accumulation of superoxide anions (O₂ ⁻) induced by light stress. Spm seems to be more effective than Spd in preserving PSI photo-stability. The correlation of the extent of PSI protection, photosystem II (PSII) inhibition and O₂ ⁻ generation with increasing Spm doses revealed that PSI photo-protection is assumed by two mechanisms depending on the PAs concentration. Given their antioxidant character, PAs scavenge directly the O₂ ⁻ generated in thylakoid membranes at physiological concentration (1 mM). However, for non-physiological concentration, the ability of PAs to protect PSI is due to their inhibitory effect on PSII electron transfer.     

Binding Sites of the Polyamines Putrescine,Cadaverine, Spermidine and Spermine on A- and B-DNA Located by Simulated Annealing

Abstract

Molecular dynamics simulations with simulated annealing are performed on polyamine-DNA systems in order to determine the binding sites of putrescine, cadaverine, spermidine and spermine on A- and B-DNA. The simulations either contain no additional counterions or sufficient Na⁺ ions, together with the charge on the polyamine, to provide 73% neutralisation of the charges on the DNA phosphates. The stabilisation energies of the complexes indicate that all four polyamines should stabilise A-DNA in preference to B-DNA, which is in agreement with experiment in the case of spermine and spermidine, but not in the case of putrescine or cadaverine. The major groove is the preferred binding site on A-DNA of all the polyamines. Putrescine and cadaverine tend to bind to the sugar-phosphate backbone of B-DNA, whereas spermidine and spermine occupy more varied sites, including binding along the backbone and bridging both the major and minor grooves.     

Duplication and Diversification of the Spermidine/Spermine N1-acetyltransferase 1 Genes in Zebrafish

Spermidine/spermine N¹-acetyltransferase 1 (Ssat1) is a key enzyme in the polyamine interconversion pathway, which maintains polyamine homeostasis. In addition, mammalian Ssat1 is also involved in many physiological and pathological events such as hypoxia, cell migration, and carcinogenesis. Using cross-genomic bioinformatic analysis in 10 deuterostomes, we found that ssat1 only exists in vertebrates. Comparing with mammalian, zebrafish, an evolutionarily distant vertebrate, contains 3 homologous ssat1 genes, named ssat1a, ssat1b, and ssat1c. All zebrafish homologues could be transcribed and produce active enzymes. Despite the long history since their evolutionary diversification, some features of human SSAT1 are conserved and subfunctionalized in the zebrafish family of Ssat1 proteins. The polyamine-dependent protein synthesis was only found in Ssat1b and Ssat1c, not in Ssat1a. Further study indicated that both 5′ and 3′ sequences of ssat1b mediate such kind of translational regulation inside the open reading frame (ORF). The polyamine-dependent protein stabilization was only observed in Ssat1b. The last 70 residues of Ssat1b were crucial for its rapid degradation and polyamine-induced stabilization. It is worth noting that only Ssat1b and Ssat1c, but not the polyamine-insensitive Ssat1a, were able to interact with integrin α9 and Hif-1α. Thus, Ssat1b and Ssat1c might not only be a polyamine metabolic enzyme but also simultaneously respond to polyamine levels and engage in cross-talk with other signaling pathways. Our data revealed some correlations between the sequences and functions of the zebrafish family of Ssat1 proteins, which may provide valuable information for studies of their translational regulatory mechanism, protein stability, and physiological functions.     

Effect of Exogenous Putrescine, Spermidine, and Spermine on K Uptake and H Extrusion through Plasmamembrane in Maize Root Segments

The action of exogenous polyamines (putrescine, spermidine, and spermine) on `washing' and fusicoccin-stimulated K⁺ uptake and H⁺ extrusion through the plasmamembrane in maize (Zea mays L., hybrid line Plenus S 516) root apical segments was studied. The results showed that polyamines inhibit the washing-stimulated K⁺ influx and H⁺ extrusion without interfering with K⁺ uptake and H⁺ extrusion stimulated by fusicoccin. Spermidine appeared to be the most effective in inhibiting K⁺ uptake and H⁺ extrusion while putrescine showed a smaller inhibiting action with respect to the others. The analysis of kinetic constants indicated that the polyamines behave as competitive inhibitors with respect to K⁺.     

Kinetic Properties of Fungal Polyamine Oxidases and Their Application to Differential Determination of Spermine and Spermidine

Polyamine oxidase from Penicillium chrysogenum oxidized spermine rapidly and spermidine slightly at pH 7.5. The apparent Km values for spermine and spermidine were calculated to be 2.25 × 10^?5 m and 9.54 × 10^?6 m, respectively. The relative maximum velocities for spermine and spermidine were 3.37 × 10^?3 m (H₂O₂) per min per mg of protein and 2.08 × 10^?4 m (H₂O₂) per min per mg of protein, respectively. Spermine oxidation of the enzyme was competitively inhibited by spermidine and putrescine. The apparent Ki values by spermidine and putrescine were calculated to be 3.00 × 10^?5 m and 1.80 × 10^?8 m, respectively. On the other hand, polyamine oxidase from Aspergillus terreus rapidly oxidized both spermidine and spermine at pH 6.5. The apparent Km values for spermidine and spermine were 1.20 × 10^?8 m and 5.37 × 10^?7 m, respectively. The relative maximum velocities for spermidine and spermine were 1.55 × 10^?2 m (H₂O₂) per min per mg of protein and 6.20 × 10^?3 m (H₂O₂) per min per mg of protein, respectively.

Differential determination of spermine and spermidine was carried out using the two enzymes. The initial rate was assayed with Penicillium enzyme and the end point was measured afte addition of Aspergillus enzyme. Small amounts of polyamines (25 to 200 nmol of spermine and 25 to 250 nmol of spermidine) were assayed by solving two simultaneous equations obtained from the rate assay method and the end point assay method. The calculated values were in close agreement with those obtained by an amino-acid analyzer.