杂交稻核酮糖二磷酸羧化酶的动力学性质

在ｐＨ８．０和３０Ｃ的条件下测定了杂交稻ＲｕＢＰ羧化酶的动力学常数,纯化酶测定值与粗酶快速测定值无明显差异。１２种不同组合的三系杂交稻其ＲｕＢＰ羧化酶动力学常数差不大,Ｋｍ（ＣＯ２）和Ｔｍａｘ的平均值与普通栽培品种也无显著差异。杂交稻汕优６３号ＲｕＢＰ羧化酶的动力学常数和酶蛋白含量与父本恢复系相类似,枰本不育系的Ｔｍａｘ和酶蛋白含量均较高。     

杂交稻核酮糖二磷酸羧化酶的动力学性质

在ｐＨ８．０和３０℃的条件下测定了杂交稻ＲｕＢＰ羧化酶的动力学常数,纯化酶测定值与粗酶快速测定值无明显差异。１２种不同组合的三系杂交稻（Ｆ１）其ＲｕＢＰ羧化酶动力学常数差异不大,Ｋｍ（ＣＯ２）和Ｖｍａｘ的平均值与普通栽培品种也无显著差异。杂交稻汕优６３号ＲｕＢＰ羧化酶的动力学常数和酶蛋白含量与父本恢复系相类似,而母本不育系的Ｖｍａｘ和酶蛋白含量均较高。     

光和暗条件培养的眼虫藻内RuBP羧化酶的免疫定位

应用免疫金标记技术证明,在眼虫藻和其它藻类中ＲｕＢＰ羧化酶主要分布在蛋白核部位,这与高等植物中ＲｕＢＰ羧化酶分布不同,在眼虫藻叶绿体间质中有少量ＲｕＢＰ羧化酶存在,这与高等植物中ＲｕＢＰ羧化酶的分布也有相似之处。暗中培养的眼虫藻不能形成类囊体,无ＲｕＢＰ羧化酶,无光合能力,只能进行异养代谢。     

表油菜素内酯对黄瓜子叶过氧化物酶活性和可溶性蛋白含量的影响

０．５ｍｇ／Ｌ的表油菜素内酯（ｅｐｉ－ＢＲ）能显著地促进黄瓜子叶叶绿素ａ、叶绿素ｂ的含量和叶绿素ａ／叶绿素ｂ比值的下降,表明ｅｎｉ－ＢＲ能促进子叶的衰老。从过氧化物酶（ＰＯＤ）的活性测定及同工酶谱发现ｅｐｉ－ＢＲ可提高其活性,暗示它可能通过提高子叶ＰＯＤ的活性而加速子叶叶绿素的降解。另一方面,ｅｐｉ－ＢＲ促进子时可溶性蛋白含量的下降,其中主要是ＲｕＢＰ羧化酶含量的下降,同时,ｅｐｉ－ＢＲ引起子叶游离氨基酸的累积。     

稀土离子对烟草RuBPcase的激活作用及EXFAS研究

研究了稀土离子（Ｌｎ３ ＋） 对烟草（Ｎｉｃｏｔｉａｎａ ｔａｂａｃｕｍ）１ ,５ － 二磷酸核酮糖羧化酶（ＲｕＢＰｃａｓｅ）活力的影响。结果表明,在该酶的反应体系中,用Ｌｎ３ ＋ 替代Ｍｇ２ ＋ ,烟草ＲｕＢＰｃａｓｅ 的活力随Ｌｎ３ ＋ 浓度的变化曲线呈双相效应, 即在高浓度时, Ｌｎ３ ＋ 抑制该酶活性; 低浓度的Ｌｎ３ ＋ 提高ＲｕＢＰｃａｓｅ 活性。其活化效应为轻稀土离子大于重稀土离子,但Ｌｎ３ ＋ 的活化效应低于Ｍｇ２ ＋ 。在有Ｍｇ２ ＋ 的反应体系中,Ｌｎ３ ＋ 在低浓度时也有提高ＲｕＢＰｃａｓｅ 活性的能力,提高幅度较低;而高浓度的Ｌｎ３ ＋ 显著地抑制酶活性。进一步对ＲｕＢＰｃａｓｅ － Ｌａ 二元复合物的ＥＸＦＡＳ 研究,证实Ｌａ３ ＋ 与ＲｕＢＰｃａｓｅ 氨基酸残基的Ｏ 原子键合,键长为２ ．５１?;Ｌａ３ ＋ 还与Ｓ 原子结合。最后对Ｌｎ３ ＋ 和ＲｕＢＰｃａｓｅ 相互作用的分子机制进行讨论     

杂种小麦及亲本旗叶老化过程中RubisCO特性的研究

小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．）旗叶的ＲｕＢＰｃａｓｅ活性、含量及ＲｕＢＰｏａｓｅ活性在旗叶全展或全展后１０ｄ达最大值,以后逐渐下降。与亲本相比,供试杂种小麦“麦优４号”在旗叶一生中尤其老化后期上述参数皆表现明显的杂种优势。旗叶ＲｕＢＰｃａｓｅ比活性在叶绿素缓降期保持平稳,在叶绿素速降期逐渐下降。供试杂种小麦较亲本具有较高的ＲｕＢＰ羧化酶和加氧酶活性,表明杂种小麦不仅具有较强的光合羧化作用,而且叶片光合作用过程中的光呼吸也较强。结果与旗叶ＲｕｂｉｓＣＯ亲合ＣＯ２和Ｏ２的动力学常数的测定结果相符。     

芦苇叶中Rubisco对干旱生境的响应

从分布于甘肃省河西走廓的沼泽芦苇和沙丘芦苇叶中提纯的Ｒｕｂｉｓｃｏ,大、小、小亚基分子量无明显变化,但沙丘芦苇与沼泽芦苇与沼泽芦苇相比较,Ｒｕｂｉｓｃｏ的氨基酸组成中,亲水性氨基酸相对含量增加,疏水性氨基酸相对含量减少,酶分子的疏水性降低,且酶分子中可被ＰＣＭＢ滴定的ＳＨ基数仅为沼泽芦苇的５０％。这说明,芦苇在长期适应沙丘干旱生境过程中,其Ｒｕｂｉｓｃｏ无论在结构与功能上,均发生有适应性的改变。     

气相色谱法测定RuBp羧化酶活性的研究

ＲｕＢｐ羧化酶作用后反应体系中能为加入的ＨＣｌ释放出的剩余,作为ＲｕＢｐ羧化酶活性指示。所释放的ＣＯ＿２以气相色谱法检测,用黄瓜叶片中ＲｕＢｐ羧化酶的反应时间曲线和酶量曲线验征,并与现行的分光光度,￣（１４）Ｃ标记测试方法比较分析,认为本方法具有应用简便、快速、准确、重复性好等优点。所以,可被认为是一种有效的测定ＲｕＢｐ羧化酶活性的方法。     

Rht3基因及带有Rht3基因的4B染色体对普通小麦光合碳同化特性的影响

本文系统地研究了带有Ｒｈｔ３基因的４Ｂ染色体二体（宁矮１号）、单体（宁矮１号Ｍ４Ｂ）、缺体（宁矮１号Ｎ４Ｂ）材料的光合特性,发现带有Ｒｈｔ３基因的４Ｂ染色体对光合速率、叶绿素含量、ＲｕＢＰ羧化酶含量及活性、叶片导度均有正效应,并有累加作用,而且对叶绿素含量缓降期和光合速率高值持续期也有正效应,因此带有Ｒｈｔ３基因的４Ｂ染色体具有促进光合作用的效应。对具有不同Ｒｈｔ３基因剂量的矮秆系（宁矮１号,即苏麦３号的Ｒｈｔ３矮秆等基因系）、半矮秆系（ＭＤ苏麦３号）及其苏麦３号的光合碳同化特性的研究,发现Ｒｈｔ３基因对光合速率、叶绿素含量、叶片导度具有正效应,但对于ＲｕＢＰ羧化酶含量和活性、叶绿素含量缓降期、光合速率高值持续期有负效应。     

黄河三角洲不同生态型芦苇对盐度适应生理的研究——Ⅱ.不同生态？…

黄河三角洲不同生态型芦苇光合速率和气孔导度有明显差异,随生境盐度的增加而降低,气孔限制因素是盐迫下芦苇光合降低的原因之一。低盐度生境中生长的芦苇的ＲｎＢＰＣａｓｅ活性均大于高盐度下的,而ＰＥＰＣａｓｅ活性均小于高盐度下的,表明在盐渍条件下,叶肉光合器官光合活 的氏也限制芦苇的光合速率。随盐度升高,ＲｕＢＰＣａｓｅ与ＰＥＰＣａｓｃ活性之比降低。高ＰＥＤ下,盐胁迫加剧Ｆｖ／Ｆｍ降低程度。此外,在高盐度     

Abscisic Acid Simultaneously Decreases Carboxylation Efficiency and Quantum Yield in Attached Soybean Leaves

Injecting abscisic acid (ABA) into the petiole of attached soybeanleaves simultaneously decreased quantum yield and carboxylationefficiency. These decreases were proportional to the accompanyingdecrease of light-saturated photosynthetic rate under normalatmosphere. ABA did not affect the CO² compensation point atsaturating irradiance, or the stimulation of net photosynthesisproduced when the partial pressure of oxygen was reduced from210 to 20 mPa Pa^–1 at a rate-limiting irradiance. Thedecreased carboxylation efficiency could not be attributed toa deactivation of RuBP carboxylase since the activation statusof the enzyme in leaves was insensitive to ABA. Although photosyntheticcapacity was decreased, the content of RuBP present was increasedin leaves treated with ABA at saturating irradiance and normalatmosphere. The increase in RuBP content was proportional tothe corresponding inhibition of photosynthetic capacity. Followingexposure to incident irradiances close to the light compensationpoint, the photosynthetic rate of ABA-treated leaves did notincrease when exposed to a subsequent increase of irradiancein the light-limited range. This response was not due to stomatalclosure. Key words: Abscisic acid, quantum yield, RuBP, RuBP carboxylase, carboxylation efficiency     

Taxonomic variation in the subunit amino acid compositions of RuBP carboxylases from grasses

Subunits of purified RuBP carboxylase extracted from 44 grass species (39 genera) have been analysed and compared in terms of MWs, amino acid compositi     

Molecular and catalytic properties of ribulose 1,5-bisphosphate carboxylase from the photosynthetic extreme halophile Ectothiorhodospira halophila.

D-Ribulose 1,5-bisphosphate (RuBP) carboxylase has been purified from the photosynthetic extreme halophile Ectothiorhodospira halophila. Despite a growth requirement for almost saturating sodium chloride in the medium, both crude and homogeneous preparations of RuBP carboxylase obtained from this organism were inhibited by salts. Sedimentation equilibrium analyses showed the enzyme to be large (molecular weight: 601,000). The protein was composed of two types of polypeptide chains of 56,000 and of 18,000 daltons. The small subunit appeared to be considerably larger than the small subunit obtained from the RuBP carboxylase isolated from Chromatium, an organism related to E. halophila. Amino acid analyses of hydrolysates of both E. halophilia and Chromatium RuBP carboxylases were very similar. Initial velocity experiments showed that the E. halophila RuBP carboxylase had a Km for ribulose diphosphate of 0.07 mM and a Km for HCO3- of 10 mM. Moreover, 6-phospho-D-gluconate was found to markedly inhibit the E. halophila carboxylase; a Ki for phosphogluconate of 0.14 mM was determined.     

Activity and activation state of ribulose-1,5-bisphosphate carboxylase of spruce trees with varying degrees of damage relative to the occurrence of novel forest decline

The aim was to determine whether a reduced carboxylation efficiency in needles of damaged spruce trees (Picea abies), is derived from a direct impairment of the ribulose-1,5-bisphosphate carboxylase (RuBP carboxylase) or there is an indirect inhibition of the RuBP carboxylase. In 1985, 1986 and 1987 measurements of RuBP carboxylase activity were carried out at three locations. Trees of different ages and degrees of damage were examined. RuBP carboxylase was assayed using both a rapid extraction method to determine the initial activity and an in vitro test after total activation to determine the total activity. The activation state was calculated as the ratio of initial activity to total activity.Within three vegetation periods the total activity in needles of damaged and apparently healthy or slightly damaged spruce trees indicated no definite difference in the annual average. On the other hand, in damaged needles a continued decline of the actual activation of RuBP carboxylase was established. The observation of continued depression of the activation state of the enzyme in needles of damaged spruce trees can possibly be due to a reduced photosynthetic electron transport rate.The measurements of the soluble protein content indicate a tendency to increased amounts in the needles of damaged trees. In accordance, a considerable increase of the activity of some enzymes like glutamine synthethase, phosphoenol-pyruvate carboxylase, and catalase could be noticed. However, there is no clear connection between the RuBP carboxylase and the content of soluble proteins.Abbreviations chl chlorophyll a+b, dw-dry weight, i.a-initial activity - P-700 reaction center of photosystem I - PVP polyvinylpyrrolidone 25 - RuBP ribulose-1,5-bisphosphate - RuBPCase ribulose-1,5-bisphosphate carboxylase - t.a. total activity     

RuBP carboxylase activity in wheat following ear emergence and evaluation of the role of ear

Ribulose bisphosphate carboxylase activity and chlorophyll content were measured in the leaves and reproductive parts of two wheat cultivars after ear emergence. The chlorophyll content of the flag leaf was mostly higher than that of the awns and glumes. Awns had the highest chlorophyll content among reproductive parts. Light transmission to the lower leaves was higher in the dwarf cultivar Moti than in the medium tall cultivar Kalyansona. RuBP carboxylase activity in Kalyansona leaves was higher than in Moti leaves. In postanthesis stages there was no difference in RuBP carboxylase activity in the flag leaf and lower leaves between cultivars. Awns had the maximum activity of RuBP carboxylase followed by glumes and grains among ear parts. The relative capacity for photosynthesis in the ear parts was several times higher than in the flag leaf on a unit chlorophyll basis. It is suggested that in a crop canopy in the field, the spike(ear) may have a greater importance in grain development than has been previously estimated.     

Degradation of ribulose-1,5-bisphosphate carboxylase and chlorophyll in senescing barley leaf segments triggered by jasmonic acid methylester, and counteraction by cytokinin

Barley ( Hordeum vulgare L. cv. Salome) primary leaf segments responded to the application of a putative plant growth regulator, ± jasmonic acid methylester (JA-Me). with accelerated senescence, as indicated by the loss of chlorophyll and the rapid decrease in activity and immunoreactive protein content of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBP carboxylase, EC 4.1.1.39). The senescence-promoting action of JA-Me differed in light and in darkness; e.g. the initial rates of chlorophyll and RuBP carboxylase breakdown were markedly higher in light than in darkness in the presence of 4.10⁻⁵ M JA-Me. Cytokinin (benzyladenine, 4.10⁻⁵ M ) stopped the loss of chlorophyll and RuBP carboxylase during senescence; however, the rapid drop induced by JA-Me in the early phase of leaf segment senescence could not be prevented by concomitant or previous addition of BA. On the other hand, BA added 24 h after JA-Me application resulted in a recovery of chlorophyll and RuBP carboxylase at the later stages, indicating a possible rapid inactivation of JA-Me in the tissues. The activities of a number of other chloroplastic and cytosolic enzymes were not significantly altered in JA-Me-treated leaf segments compared with controls floated on water. Time-dependent chlorophyll decrease in isolated chloroplasts did not change upon JA-Me addition to the isolated organelles. It is suggested that JA-Me acts on chloroplast senescence by promoting cytoplasic events which eventually bring about the degradation of chloroplast constituents.     

Activity and quantity of ribulose bisphosphate carboxylase-and phosphoenolpyruvate carboxylase-protein in two Crassulacean acid metabolism plants in relation to leaf age,nitrogen nutrition,and point in time during a day/night cycle

Activity of ribulose 1,5-bisphosphate (RuBP) carboxylase in leaf extracts of the constitutive Crassulacean acid metabolism (CAM) plant Kalanchoe pinnata (Lam.) Pers. decreased with increasing leaf age, whereas the activity of phosphoenolpyruvate (PEP) carboxylase increased. Changes in enzyme activities were associated with changes in the amount of enzyme proteins as determined by immunochemical analysis, sucrose density gradient centrifugation, and SDS gel electrophoresis of leaf extracts. Young developing leaves of plants which received high amounts of NO ₃ ^- during growth contained about 30% of the total soluble protein in the form of RuBP carboxylase; this value declined to about 17% in mature leaves. The level of PEP carboxylase in young leaves of plants at high NO ₃ ^- was an estimated 1% of the total soluble protein and increased to approximately 10% in mature leaves, which showed maximum capacity for dark CO₂ fixation. The growth of plants at low levels of NO ₃ ^- decreased the content of soluble protein per unit leaf area as well as the extractable activity and the percentage contribution of both RUBP carboxylase and PEP carboxylase to total soluble leaf protein. There was no definite change in the ratio of RuBP carboxylase to PEP carboxylase activity with a varying supply of NO ₃ ^- during growth. It has been suggested (e.g., Planta 144, 143–151, 1978) that a rhythmic pattern of synthesis and degradation of PEP carboxylase protein is involved in the regulation of -carboxylation during a day/night cycle in CAM. No such changes in the quantity of PEP carboxylase protein were observed in the leaves of Kalanchoe pinnata (Lam.) Pers. or in the leaves of the inducible CAM plant Mesembryanthemum crystallinum L.Abbreviations CAM Crassulacean acid metabolism - RuBP ribulose 1,5-bisphosphate - PEP phosphoenolpyruvate - G-6-P glucose-6-phosphate     

Relation between Nitrogen and Ribulose-1,5-bisphosphate Carboxylase in Rice Leaves from Emergence through Senescence

The relation between N content and ribulose-l,5-bisphosphate(RuBP) carboxylase protein was examined in the 12th leaf bladeof rice. Plants were grown under different amounts of N afterthe emergence of the 12th leaf blade. RuBP carboxylase proteinincreased with leaf N during leaf expansion. The synthesis ofRuBP carboxylase predominated during this period, and changesin the amounts of carboxylase synthesized until leaf death paralleledchanges in the N influx to the leaves. When the carboxylasereached its maximum content, the proportion of RuBP carboxylaseto leaf N was 27 to 28% irrespective of N treatment. As theleaf senesced, however, this proportion differed significantlywith the treatment. It was higher in the N-deficient leaf thanin the N-sufficient leaf. This was due to different patternsof RuBP carboxylase degradation for the treatments during senescence.RuBP carboxylase was degraded actively during the early stageof senescence in the N-sufficient leaf, whereas its degradationproceeded almost constantly in the N-deficient leaf during senescence. (Received October 17, 1983; Accepted January 27, 1984)     

Proteolysis of ribulose-1,5-bisphosphate carboxylase/oxygenase in Citrus leaf extracts

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBP carboxylase, EC 4.1.1.39) has been purified from orange [ Citrus sinensis (L.) Osbeck cv. Washington Navel] leaves using sucrose gradient centrifugation in a fixed angle rotor. Following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), two major bands corresponding to the two subunits of RuBP carboxylase were found. The large subunit coincided with the polypeptide band that has been previously reported to be preferentially mobilized during the spring and summer flush periods.
The degradation of RuBP carboxylase during autodigestion of Citrus leaf extracts, investigated by SDS-PAGE, occurred mainly at acidic (2.5-5.5) pH. The two subunits showed differences in the rate of degradation, the smaller being more rapidly hydrolyzed than the larger. At least four proteolytic activities were identified by means of inhibitor experiments: 1) a pepstatin A-sensitive activity that acts on both RuBP carboxylase subunits, 2) a mercurial ( p -hydroxymercuribenzoate and p -chloromercuriphenylsulfonate)-sensitive activity that degrades only the small subunit, 3) an EDTA-sensitive activity that hydrolyzes both the large and small subunits, and 4) a mercurial-stimulated activity that acts only on the large subunit. It is suggested that the last two proteases may be responsible for the degradation of RuBP carboxylase observed in vivo during the periods of mobilization of leaf protein in Citrus .     

Variations in Kinetic Properties of Ribulose-1,5-bisphosphate Carboxylases among Plants

Studies of ribulose-1,5-bisphosphate (RuBP) carboxylase from taxonomically diverse plants show that the enzyme from C(3) and crassulacean acid metabolism pathway species exhibits lower K(m)(CO(2)) values (12-25 micromolar) than does that from C(4) species (28-34 micromolar). RuBP carboxylase from aquatic angiosperms, an aquatic bryophyte, fresh water and marine algae has yielded consistently high K(m)(CO(2)) values (30-70 micromolar), similar in range to that of the enzyme from C(4) terrestrial plants. This variation in K(m)(CO(2)) is discussed in relation to the correlation between the existence of CO(2)-concentrating mechanisms for photosynthesis and the affinity of the enzyme for CO(2). The K(m)(RuBP) of the enzyme from various sources ranges from 10 to 136 micromolar; mean +/- sd = 36 +/- 20 micromolar. This variation in K(m)(RuBP) does not correlate with different photosynthetic pathways, but shows taxonomic patterns. Among the dicotyledons, the enzyme from crassinucellate species exhibits lower K(m)(RuBP) (18 +/- 4 micromolar) than does that from tenuinucellate species (25 +/- 7 micromolar). Among the Poaceae, RuBP carboxylase from Triticeae, chloridoids, andropogonoids, Microlaena, and Tetrarrhena has yielded lower K(m)(RuBP) values (29 +/- 11 micromolar) than has that from other members of the grass family (46 +/- 10 micromolar).