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Biomedical subjects

C F Thurston

Publications and source records attributed to C F Thurston.

28 records · Page 2Linked to original sources
PubMed1978

Control of isocitrate lyase synthesis in Chlorella fusca var. vacuolata. Rate of enzyme synthesis in the presence and absence of acetate measured by [35S]methionine labelling and immunoprecipitation.

The rate of increase of isocitrate lyase activity was measured in darkened Chlorella fusca var. vaculoata cultures in the presence and absence of acetate and compared with the rate of incorporation of [35S]methionine into isocitrate lyase enzyme protein under the same conditions. Isocitrate lyase enzyme protein was isolated for this purpose by specific immunoprecipitation and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. After 4h in the dark, in the presence of acetate the rate of increase of isocitrate lyase activity was 75 times that in the absence of acetate. Incorporation of [35S]methionine into isocitrate lyase was 140 times greater in the presence of acetate. Incorporation of [35S]methionine into the trichloroacetic acid-insoluble fraction overall was about five times as fast in the presence of acetate. These data are not consistent with an increased turnover of isocitrate lyase enzyme molecules, sufficient to account for the low rate of increase of isocitrate lyase activity in the absence of acetate. The greater rate of enzyme synthesis in the presence of acetate must therefore be due to some effect of this metabolite on the processing or translation of isocitrate lyase mRNA.

Acetates↗
PubMed1977

Simultaneous operation of three catabolic pathways in the metabolism of glucose by Thiobacillus A2.

Enzymes essential to the operation of the Embden-Meyerhof glycolytic pathway, the Entner-Duodoroff pathway and oxidative pentose phosphate pathway were present in Thiobacillus A2 grown on glucose and other sugars. Radiorespirometry under various conditions with Thiobacillus A2 oxidising glucose specifically labelled with 14C in carbon atoms 1, 2, 3, 3 + 4, 6 or universally labelled demonstrated the simultaneous operation of the Embden-Meyerhof (48%), Entner-Doudoroff (28%), and pentose phosphate (24%) pathways in release of carbon dioxide from glucose. Growth on succinate, or autotrophically on formate or thiosulphate resulted in repression of most enzymes of the pathways, but high aldolase levels were retained indicating its role in gluconeogenesis and the Calvin cycle. Different fructose diphosphatase activities were found in succinate- and thiosulphate-grown organisms. The results indicate that all three major catabolic pathways for glucose function in Thiobacillus A2 grown on sugars. Thiobacillus acidophilus showed a different radiorespirometric pattern and apparently used the Entner-Duodoroff (64.5%) and pentose phosphate (35.5%) pathways, but showed unusually high release of carbon atom 6, as was also found for T. ferrooxidans.

Arsenic↗
PubMed1977

Control of isocitrate lyase synthesis in Chlorella fusca var. vacuolata. The basal activity of the enzyme and the kinetics of induction.

1. Isocitrate lyase activity was measured in non-induced Chlorella fusca var. vacuolata cells. 2. During exponential autotrophic growth about 1-2 molecules of the enzyme per cell were present. 3. In light-limited cultures the amount of the enzyme increased to 10-20 molecules/cell. 4. When autotrophic cultures were placed in the dark, the basal activity of isocitrate lyase increased after a 2h lag so that after 8h in the dark there was a 500-fold increase in activity. 5. When isocitrate lyase was induced (by addition of acetate and removal of illumination) in autotrophic cultures which had been growing exponentially, the full induced rate of enzyme synthesis was obtained after 70-80min. 6. When light-limited autotrophic cultures were induced, the rate of isocitrate lyase synthesis was maximal after only 40-50min. 7. These data are consistent with a catabolite-repression control co-ordinated with photosynthetic activity,which may be independent of the specific inducing effect of acetate.

Acetates↗
PubMed1975

The kinetic of degradation of chondroitin of sulphates and hyaluronic acid by chondroitinase form Proteus vulgaris.

Km and Vmax. were determined for the degradation by chondroitinase of chondroitin 4-sulphate, 4-sulphate-proteoglycna, chondroitin 6-sulphate, dermatan sulphate and hyaluronic acid. Degradation of chondroitin 4-sulphate was inhibited by hyaluronic acid but not by keratan sulphate. The results are discussed with regard to the use to the use of chondroitinase as a sleective reagent for the degradation of tissue glycosaminoglycans.

Chondroitin↗
PubMed1975

Characterization and messenger activity of poly(A)-containing RNA from Chlorella.

Poly(A)-containing RNA was isolated by cellulose column chromatography from total RNA extracted from Chlorella fusca var. vacuolata 211/8p. RNA retained by the column was identified as poly(A)-containing RNA because it contained ribonuclease-resistant tracts, 25 to 55 nucleotides in length, from which not less than 80% of base was found to be adenine after acid hydrolysis. The base composition of poly(A)-containing RNA differed from that of RNA (largely ribosomal) which did not adsorb to cellulose, having a higher adenine content and a lower guanine content. Poly(A)-containing RNA was polydisperse including molecules with mobilities from 10S to 40S with a mean of about 20S. In an in vitro system derived from wheat-germ, protein synthesis was stimulated by adding poly(A)-containing RNA from Chlorella. Optimum conditions were established in this system with respect to the amount of poly(A)-containing RNA added and the concentration of KCl and Mg-2+. It is proposed that, in Chlorella, poly(A)-containing RNA includes cytoplasmic mRNA as has been shown for some other eucaryotic organisms.

Adenine Nucleotides↗
PubMed1970

Disappearance of isocitrate lyase enzyme from cells of Chlorella pyrenoidosa.

1. When acetate-adapted cells of Chlorella are suspended in nitrogen-free medium and supplied with glucose, isocitrate lyase activity disappears from the cells at a rate of about 9%/h. This loss of activity is shown to be accompanied by loss of isocitrate lyase protein. 2. When isocitrate lyase activity is assayed in intact cells after freezing and thawing, the rate of loss of activity after addition of glucose approaches 20%/h. 3. It is shown, by using (35)S, that the rate of turnover of isocitrate lyase protein is somewhat lower than that of other major soluble proteins; general protein turnover during nitrogen starvation, and after glucose addition, is too slow to account for the rate of loss of isocitrate lyase protein. 4. Disappearance of isocitrate lyase activity must result from a mechanism that allows degradation of this specific protein under conditions of limiting nitrogen supply.

Acetates↗