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D Lloyd

Publications and source records attributed to D Lloyd.

At least 307 records · Page 17Linked to original sources
PubMed1968

Electron transport in mitochondria isolated from the flagellate Polytomella caeca.

1. Mitochondria isolated from Polytomella caeca contain cytochromes b, c+c(1) and a+a(3) and several flavoprotein species. 2. Electron transport is inhibited by antimycin A, rotenone, piericidin A and cyanide. 3. Spectral data indicate that antimycin A inhibits the reoxidation of reduced cytochrome b. 4. Various types of flavoprotein are characterized by simultaneous spectrophotometric and fluorimetric measurements on antimycin A-inhibited preparations and also by their absorption and fluorescence-emission spectra. 5. The rotenone-sensitive site lies between the two flavoproteins of the respiratory chain, designated FpD1 and FpD2. 6. Other flavoprotein species detected include those involved in the oxidation of succinate and externally added NADH; a large proportion of mitochondrial flavine is reduced by dithionite but not by known respiratory substrates. 7. The kinetics of flavoprotein and cytochrome reactions were studied.

Journal Article↗
PubMed1968

Propionate assimilation in the flagellate Polytomella caeca. An inducible mitochondrial enzyme system.

1. The assimilation of propionate by Polytomella caeca involves the beta-oxidation of this fatty acid. 2. Propionate-grown cells immediately oxidize propionate, beta-hydroxypropionate, malonic semialdehyde and acetate; acetate-grown cells oxidize propionate rapidly only after a lag of 2hr., and this adaptation of resting cells to propionate involves the formation of the enzymes of beta-oxidation. 3. The beta-hydroxypropionate dehydrogenase and malonic semialdehyde dehydrogenase activities of both propionate-grown and propionate-adapted cells are partly located in mitochondrial fractions. 4. Mitochondria isolated from propionate-grown cells, and also those from acetate-grown cells fully adapted to propionate, oxidize succinate, alpha-oxoglutarate, beta-hydroxypropionate and malonic semialdehyde; oxidation of these substrates is tightly coupled to the phosphorylation of ADP. 5. Mitochondria from acetate-grown cells exhibit ADP-dependent oxidation of succinate and alpha-oxoglutarate, but do not oxidize beta-hydroxypropionate or malonic semialdehyde. Mitochondria isolated from acetate-grown cells adapted to propionate for 5hr. slowly oxidize beta-hydroxypropionate and malonic semialdehyde, but no tightly coupled phosphorylation is detectable. 6. Two of the inducible enzymes of propionate oxidation are located within the NAD-impermeable barrier and appear to be membrane-bound. 7. The formation of the inducible enzymes is inhibited by cycloheximide and actinomycin D, but not by chloramphenicol.

Acetates↗
PubMed1967

The regulation of propionate oxidation in Prototheca zopfii.

1. Whole cell suspensions of Prototheca zopfii grown on propionate oxidize propionate, acrylate, malonic semialdehyde and acetate immediately, whereas acetate-grown cells only oxidize acrylate or propionate rapidly after a lag of 20-30min. This adaptation to propionate is slowed down by 8-azaguanine or p-fluorophenylalanine, and is not influenced by adding an ammonium salt or an amino acid mixture. 2. The adaptation involves induction of the enzymes of beta-oxidation of propionate. 3. A small proportion (5-8%) of the activities of propionyl-CoA dehydrogenase, beta-hydroxypropionate dehydrogenase and malonic semialdehyde dehydrogenase are consistently associated with mitochondria isolated from propionate-grown cells. 4. Such mitochondria will oxidize propionyl-CoA, beta-hydroxypropionate and malonic semialdehyde, and the respiration rates with these substrates in the presence of inorganic phosphate are ADP-dependent. 5. Mitochondria from acetate-grown cells do not contain detectable activities of the enzymes of propionate oxidation.

Acetates↗
PubMed1965

The purification and properties of malonic semialdehyde oxidative decarboxylase from Prototheca zopfii.

1. An enzyme, which in the presence of NAD(+) and CoA oxidizes malonic semialdehyde to acetyl-CoA, has been purified from an extract of the colourless alga Prototheca zopfii. 2. The purified enzyme has optimum pH7.5, is specific for NAD(+) and requires a thiol compound for maximum activity. 3. The enzyme is inhibited by arsenite, N-ethylmaleimide and urea. 4. The results are discussed in relation to those obtained by other workers with a similar bacterial enzyme, and a possible reaction sequence is proposed.

Arsenicals↗
PubMed1965

The assimilation of acetate and propionate by Prototheca zopfi.

1. The tricarboxylic acid and glyoxylate cycles are of major importance in the assimilation of acetate and propionate by Prototheca zopfii. The pattern of assimilation of [2-(14)C]acetate and [2-(14)C]propionate by whole cells growing with their respective substrates is similar except that, with propionate, beta-hydroxypropionate is the first labelled intermediate detected. 2. Carbon dioxide fixation is of little quantitative importance for the growth of this organism with propionate. 3. The yield of cells obtained/mole of acetate is similar to that obtained/mole of propionate and about half that obtained/mole of n-butyrate, these substrates acting as sole sources of carbon and energy.

Journal Article↗
PubMedDate not supplied

Immunochemical localization of the small leucine-rich proteoglycan lumican in human predentine and dentine.

The immunocalization of the small interstitial leucine-rich keratan sulphate proteoglycan lumican was studied in human teeth using a polyclonal antibody towards lumican and a standard indirect peroxidase technique. There was intense labelling for lumican in predentine, with immunopositivity also observed in and around the tubules, around the odontoblasts and in the pulp with a fibrillar distribution. The previous reported ability of lumican to control collagen fibrillogenesis and it putative function in collagen spacing suggest potential roles for lumican in predentine in relation to mineralization.

Adolescent↗