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- A phenolic pigment was extracted from baker's yeast. The pigmentis slowly autooxidizable, and rapidly oxidized with Rhus-laccaseor polyphenol oxidase and reduced by dithionite.
- The pigmentdissolved in ethylether had an absorption peak at258 mµ,shoulders at 289 and 382 mµ and a plateauat 450500mµ. The difference spectrum between oxidizedand reducedforms of the pigment showed a wide plateau around500 mµ.
- The pigment supported the oxygen uptake by reconstructed enzymesystem: L-lactate, L-lactate cytochhrome c reductase and Rhuslaccaseor polyphenol oxidase. In its absence, no oxygen uptake tookplace. The pigment was replaced successfully with p-quinone,catechol and menadione, but not with ubiquinone. The sequenceof hydrogen transport can be represented: L-lactate L-lactatecytochrome c reductase "phenolic pigment" oxidase oxygen.
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LIDA XING PHIL R. BELL PHILIP J. CURRIE MASATERU SHIBATA KUOWEI TSENG ZHIMING DONG 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2012,45(4):500-506
Xing, L, Bell, P.R., Currie, P.J., Shibata, M., Tseng, K. & Dong, Z. 2012: A sauropod rib with an embedded theropod tooth: direct evidence for feeding behaviour in the Jehol group, China. Lethaia, Vol. 45, pp. 500–506. A fragmentary rib from the Lower Cretaceous (Barremian) Yixian Formation in northeastern China preserves rare, direct evidence of feeding behaviour by an unidentified theropod. The rib, which comes from the holotype of Dongbetitan, preserves an embedded, broken theropod tooth. Comparison of the tooth with all known theropods from the Yixian Formation suggests that it belongs to a new taxon of medium‐sized theropod. Given the large size difference between the sauropod and the theropod and the absence of reactive bone growth around the tooth, the bite likely occurred post‐mortem during scavenging. Recognition of a new, medium‐sized theropod increases the known diversity of taxa from the Yixian Formation and helps fill a gap in the theropod palaeoecology of that formation, which previously consisted of only small (<2 m) forms. □China, Cretaceous, feeding behaviour, theropod, titanosauriformes, sauropod. 相似文献
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- 1) When yeast cells grown anaerobically were adapted to aerobicculture in a normal medium, catalase formation was markedlyenhanced after the earlier stage of exponential growth of thecells. The same thing occurred with cells transferred from ananaerobic culture into a nitrogen deficient medium.
- 2) Thecatalase activity of aerobically grown cells declinedprogressivelyuntil glucose, which had been added to the mediumwas profoundlyexhausted. This decline was followed by a progressiverecoveryof activity to a normal level with the growth of thecells.Similar behavior of catalase was also seen at low concentrationsof glucose, except that an abrupt rise in activity was observedat the beginning of incubation. Even when cells which had declinedto a minimum of catalase activity were aerated in phosphatebuffer, they continued to synthesize catalase.
- 3) The patternof alteration of catalase activity during cellgrowth was accompaniedby a comparable pattern of alterationin respiratory capacity.On the basis of this finding, togetherwith the fact that antimycinA causes intensive depression incatalase formation, it maybe inferred that the formation ofthe respiratory chain conductsthe formation of catalase.
- 4) In the presence of ethyl alcoholas the carbon source inplace of glucose, a rise in both catalaseactivity and respiratorycapacity occurred from initiation ofincubation. This fact canbe interpreted to mean that the repressiveeffect of glucoseon catalase formation depends on the aerobiccharacter of thecells.
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Photosynthetic nitrite reductase (PNiR) was purified extensivelyfrom spinach leaves by the method including acetone precipitation,ammonium sulfate fractionations and DEAE-cellulose column chromatography.The purified PNiR had the highest specific activity thus farobtained. Absorption spectrum of the purified PNiR indicatedthat it had no flavin component. There was no difference inthe rate of photosynthetic nitrite reduction between aerobicand anaerobic conditions. In chloroplasts two reductase systems related with ferredoxinhad been recognized, which were ferredoxin-nitrite and ferredoxin-NADPreductase system. The relationship between the two systems wasinvestigated by using the reconstituted enzyme system. Whenthe reduction of NADP was taking place, the reduction of nitritewas strongly inhibited. Some physiological significance of thephenomenon was discussed.
1This work was mainly perfomed in the Department of Cell Physiology,University of California, during the author's stay, and waspresented in the 6th annual meeting of the Japanese Societyof Plant Physiologists on April 4-7, 1964 in Tokyo. 相似文献
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- Two lactate dehydrogenases, L(+)- and D()- lactate cytochromec reductase, were extracted from the baker's yeast after disintegrationof the cells by a FRENCH press. They are separated by electrophoresison polyacrylamide gel and their activities were compared bycolor density of formazan, the reduction product of nitrobluetetrazolium.
- The ratio of L-lactate cytochrome c reductaseactivity to D-lactatecytochrome c reductase activity variedto a great extent, dependingon culture conditions. L-Lactatecytochrome c reductase waspredominant in resting cells; thereverse was the case withcells in early exponential stage ofthe growth.
- When the cells in exponential stage of growthwere aerated withoutnitrogen source, there occurred an intensiveincrease of L-lactatecytochrome c reductase, accompanied bythe decrease of D-lactatecytochrome c reductase.
- Effectsof inhibitors on the activity ratio of these two enzymeswereinvestigated. o-Phenanthroline, dinitrophenol, sodium azide,chloramphenicol, British antilewisite and antimycin A favored,in this order, the formation of L-lactate cytochrome c reductase.
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