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Sulphate activation in higher plants (1969)

Ellis, R. J.

Springer

Planta 88 (1969), S. 34-42

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ISSN: 1432-2048

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary ATP-sulphurylase was detected in extracts of roots and leaves of several species of higher plant. The enzyme occurs in the supernatant fraction, has a pH optimum of 8.0 and an absolute requirement for Mg2+ ions. Sulphurylase activity is inhibited by selenate and molybdate but not by cysteine, methionine, glutathione, or thiol reagents. The synthesis of sulphurylase by turnip, lettuce, tomato, and Lemna plants grown under aseptic conditions is neither induced by sulphate nor repressed by cystine, and in the latter respect sulphate activation in plants differs from than in micro-organisms. APS-kinase could not be detected in extracts of any tissue although its product was stable under the conditions used. Sulphate reduction in higher plants may thus proceed via adenylysulphate and not via phosphoadenylylsulphate as in many micro-organisms.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00396112

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Characterisation of amino acid incorporation by subcellular fractions from sterile beet disks (1968)

Ellis, R. J. ; MacDonald, I. R.

Springer

Planta 83 (1968), S. 248-256

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ISSN: 1432-2048

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The optimum concentrations of leucine, ATP, GTP and Mg2+ ion for the incorporation of leucine into protein by the microsomal fraction isolated from sterile disks of red beetroot are 0.06 mM, 5 mM, 0.5 mM, and 12 mM respectively. Incorporated 14C-leucine does not exchange with an excess of soluble-12C-leucine. Incorporation into protein is partly dependent on the addition of a high speed supernatant fraction which incorporates leucine into a product with the properties of aminoacyl RNA. Addition of polyuridylic acid to microsomes isolated from fresh disks stimulates the incorporation of phenylalanine into protein nine-fold but has no effect on leucine incorporation. Polyuridylic acid — stimulated incorporation is not inhibited by chloramphenicol. Preincubation of fresh microsomes with trypsin does not increase their activity. These results suggest that the low activity of fresh microsomes may be due to a lack of messenger RNA. The mitochondrial fraction shows a rise and fall in leucine-incorporating ability during aging similar to that shown by the microsomal fraction. Studies with inhibitors suggest that about 25% of this incorporation is due to the mitochondria themselves, the rest being attributable to large microsomes. Fractions isolated from disks aged under non-sterile conditions show large incorporations of leucine which are not dependent on an added energy source. This result confirms the importance of using aseptic techniques when studying the aging of storage tissue disks.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00385334

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