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Title: Studies on cytochrome P-450 in some higher plants
Author: Cottrell, Suzanne
ISNI:       0000 0001 3390 1751
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1987
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This thesis presents data obtained on the nature and roles of cytochrome P-450 in some higher plant tissues. The following were found, by spectral investigation, to have specific microsomal P-450 concentrations of the same order of magnitude as rat liver: avocado mesocarp (0. 33 nmol mg-1 protein) tulip bulb (0. 25 nmol mg-1) and Arum maculatum spadix (0. 4 nmol mg-1). Other components of the microsomal electron transfer system were detected in avocado and tulip bulb preparations. An alternative method employing polyethylene glycol and low speed centrifugation has been successfully adapted for the preparation of microsomal fractions from plant tissues. This allowed rapid microsomal preparation with high P-450 recovery and circumvented the need for ultracentrifugation of large volumes of the post-mitochondrial supernatant. Conditions were optimized for the detergent solubilisation of avocado mesocarp microsomal P-450. Partial resolution of P-450 from avocado or tulip bulb was achieved using ion-exchange and adsorption chromatography. These partially purified forms were compared electrophoretically with various P-450 forms from rat liver. Spectral binding studies showed that compared to rat liver, avocado P-450 has only a limited capacity to bind compounds. These included a range of fatty acids, N-methyl-arylamines, a range of aryl hydrocarbons, aniline, certain classical mammalian inhibitors and imidazole antifungal agents. Such studies proved a useful method of scanning for possible P-450 substrates in that good correlation exists between compounds giving type I binding spectra and metabolism. These studies also provided information as to the nature of the active site of avocado P-450. Metabolic studies showed that avocado P-450 does not possess the versatility of hepatic P-450 in metabolising xenobiotics. However evidence is presented implicating the avocado P-450 in the metabolism of lauric acid and the N-demethylation of N-methyl-arylamines. Inhibition studies suggested that these enzyme activities were independent of each other and therefore adds to the evidence for multiple P-450 forms in higher plants.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Plant cytochrome P-450