摘要:

AbstractThe quantity and quality of fractionated leaf proteins from different plant species were investigated. Leaf extracts (pH range 7.0–8.3) were prepared on a laboratory scale from greenhouse cultivated plants. The proteins were fractionated by differential centrifugation followed by gel filtration.Amaranthus caudatus and Chenopodium quinoaseem favourable for production of non‐green leaf protein concentrates, since the water‐soluble protein comprised nearly 50% of the extracted protein. The chlorophyll‐associated protein in fresh extracts from these species was, however, difficult to sediment. A practical separation of chlorophyll‐associated protein from the chlorophyll‐free proteins will require some kind of pre‐aggregation of the chlorophyll‐associated proteins.In extracts fromDactylis glomerata, Lolium perenne and Vicia sativaa considerable proportion of the extracted protein sedimented rapidly, but at least for the grasses some of the chlorophyll‐associated protein remained in the supernatants even after centrifugation at 30 000 g for 180 min. Practical separation of all the chlorophyll‐associated protein from the extract requires some kind of pre‐aggregation of the chlorophyll‐associated proteins even for these species. The situation was similar for extracts fromHelianthus annuus, but a very high percentage of the total chlorophyll‐associated proteins could be sedimented at low centrifugation speed.Brassica oleraceawas the most suitable species for the removal of the chlorophyll‐associated proteins by centrifugation alone. Moreover, the proportion of chlorophyll‐free protein in the extracts was relatively high, more than 40%.Thein vitrodigestibility of membrane‐bound protein fractions was high for species with co‐aggregation of water‐soluble proteinand membrane‐bound protein. Causes underlying the different distributions of the chlorophyll‐associated and chlorophyll‐free proteins and the reason for the different size of the chlor

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03239.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractNon‐green leaf protein concentrates can be produced after separation of chlorophyll‐associated proteins from chlorophyll‐free proteins by sedimenting the chlorophyll‐containing membranes suspended in press juice. To make the use of low speed centrifugation possible, the influence of pH on protein sedimentation rate was investigated, especially forBrassica Oleracea(17 cultivars). Press juices produced on a laboratory scale from greenhouse grown plant material were adjusted to the desired pH and centrifuges briefly at 5000 g or 15,000 g. The chlorophyll‐associated protein fromB. Oleracessedimented rapidly at pH values both below and above 6.0(original pH of the press juice). When the pH of the press juice was adjusted to 7.5, all the chlorophyll‐associated protein sedimented at 15,000 g, whereas about 45%of the original protein remained in the supernatant. An increase in sedimented chlorophyll‐associated protein at higher pH was also observed forBrassica napus, Helianthus annuusandVicia faba, but not forBeta vulgarisandDactylis glomerata.Theoretically, the protein sedimentation pattern typical forB. oleraceamight depend primarily on protein aggregation, but shrinking of thylakoids at pH values higher than 6 could contribute. The deviation from this pattern observed forB. vulgarisandD. glomeratamight be caused by differences in composition of proteins or low molecular species. In practice, a pH above 7.0 seems to be useful for separation of chlorophyll‐associated proteins from chlorophyll‐free proteins by centrifugation of press juice fromBrassicaspecies witho

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03240.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractIn the range 10−6M‐ 5 × 10−2Muptake of K+in excised roots of barley (Hordeum vulgareL. cv. Herta) with low and high K content could in both cases be represented by an isotherm with four phases. Uptake, especially in the range of the lower phases, was reduced in high K roots through decreases in Vmaxand increases in Km. Similar data for other plants are also shown to be consistent with multiphasic kinetics. The concentrations at which transitions occurred were not affected by the K status, indicating the existence of separate uptake and transition sites. Uptake was markedly reduced in the presence of 10−5M2,4‐dinitrophenol, especially at low K+concentrations, but the isotherms remained multiphasic. This contraindicates major contributions from a non‐carrier‐mediated, passive flux. A tentative hypothesis for multiphasic ion uptake envisions a structure which changes conformation as a result of all‐or‐none changes in a separate transition site. The structure is “tight” at low external ion concentrations (low Vmax. low Km. active uptake, allosteric regulation) and “loose” at high concentrations (high Vmax‐high Km‐facilit

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03241.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY