Thesis (Ph. D. in Pharmacology)--Vanderbilt University, Dec. 2005. / Title from title screen. Includes bibliographical references.

No description available.

Soybean seeds are known to contain high levels of lipoxygenase activity, especially during early stages of germination. Crude mitochondrial fractions from germinating soybeans also have been shown to exhibit high rates of cyanide-insensitive oxygen uptake. These results show the effects of successive discontinuous PercollR density gradients on mitochondrial fractions from 2 day old soybean seeds as judged by polarographic studies and Ouchterlony double diffusion. Axis mitochondria exhibited totally cyanide-sensitive oxygen uptake after two gradients and cotyledon mitochondria exhibited from none to 11% cyanide-insensitive oxygen uptake after three gradients. Mitochondrial fractions which were assayed for lipoxygenase with double diffusion exhibited positive results with fractions that showed cyanide-insensitive oxygen uptake and negative results with cyanide-sensitive mitochondria. These results suggest that lipoxygenase can loosely associate with the mitochondrial membrane and that gradient centrifugation can purify mitochondria free of both lipoxygenase and cyanide-insensitive oxygen uptake.

Graduation date: 1999

Thesis (Ph. D.)--University of Nebraska--Lincoln, 1999. / PDF text: [2] leaves abstract, vii, 105 leaves : ill. Includes bibliographical references (leaves 103-105 of dissertation).

Thesis (doctoral)--Tallinn Technical University, 2001. / Includes bibliographical references (p. 59-64).

Aspergillus niger and Penicillium candidum were grown and harvested on days 6 and 8, which corresponded to their maximal biomasses and lipoxygenase (LOX) activities. The extracts were enriched with ammonium sulfate precipitation at 30 to 70% and 20 to 60% of saturation, respectively. The LOX activity was assayed with linoleic, linolenic and arachidonic acids as substrates. Both enriched microbial LOXs demonstrated preferential substrate specificities towards free fatty acids, over acyl esters of linoleic acid. The LOXs had the highest catalytic efficiency values (ratio of V max to Km) for linolenic acid biocatalysis. Major and minor pH optima at 5.0 and 10.5 were observed for A. niger, whereas for P. candidum they were at 6.0 and 8.5. Normal phase high-performance liquid chromatography (NP-HPLC) and gas-liquid chromatography/mass spectrometry (GC/MS) characterization of end products revealed that both LOXs produced the 10-hydroperoxide of linoleic acid (10-HPOD) at 15 to 16% of total isomers detected, respectively. Chiral studies of the P. candidum LOX catalyzed hydroperoxides revealed an excess in the production of (S) stereo-isomers resultant from linoleic, linolenic and arachidonic acids bioconversion. Penicillium camemberti was grown and harvested at its maximal biomass and LOX activity. The microbial extract was ultrafiltered (30 kDa NMWCO) and KCI (7.5 ppm) was added prior to lyophilization for the stabilization of enzyme activity. The LOX and hydroperoxide lyase (HPL) activities were assayed using linoleic acid and the 10-HPOD as substrates, respectively. The post-lyophilization residual activities were 93% and 223% for LOX and HPL, respectively. The long-term storage stability (-80°C) of the extract (KCI 7.5 ppm) was ~100% after 8 and 4 weeks for LOX and HPL, respectively. The investigated stabilizing chemical additives included glycine, mannitol, glycerol, sucrose and polyethylene glycol. The lowest Kinactivation values were observed with glycine with 0.136 and 0.0296 for LOX and HPL, respectively. Thermostability studies indicated that 5 and 10% (w/v) mannitol and glycine effectively stabilized LOX and HPL, respectively. Immobilization of an enzymatic extract from P. camemberti containing LOX and HPL activities was performed on EupergitRTMC and EupergitRTMC250L-iminodiacetate (IDA), respectively. The free and immobilized extracts both possessed LOX activity with a pH optimum of 6.0, whereas pH 6.0 and 4.0 were the optima of the HPL activity for free and immobilized extract, respectively. Optimal LOX reaction temperatures were 30 and 55°C for the free and immobilized extract, respectively, whereas 45 and 30°C were determined for the HPL activity of the free and immobilized extract, respectively. Long-term stability (-80°C) of the immobilized extract containing LOX and HPL activity showed residual activities of 82.6 and 93.8% after 4 and 8 weeks, respectively.

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Betty Jean Gaffney, Florida State University, College of Arts and Sciences, Dept. of Biological Science. Title and description from dissertation home page (viewed Jan. 13, 2005). Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Susan M. Fischer. Vita. Includes bibliographical references.

No description available.