Induction and activity of the mandelate pathway enzymes in bacterium NCIB 8250

Livingstone, Alan (1970) Induction and activity of the mandelate pathway enzymes in bacterium NCIB 8250. PhD thesis, University of Glasgow.

Abstract

This thesis starts with a synopsis of the literature on the metabolism of mandelate and related compounds by microorganisms. Present knowledge of the control of these pathways is also summarised. The experimental work described in this thesis is primarily concerned with the activity and control of the enzymes converting L-mandelate and benzyl alcohol to cis, cismuconate in bacterium NCIB 8250 which is an Acinetobacter species. Techniques were worked out for mutagenesis with N-methyl-N-nitroso-N-nitroguanidine and ultraviolet irradiation. Using the former treatment, "mandelate mutants'' i.e. strains able to grow .on benzoate or benzyl alcohol but not on L-mandelate, "benzyl alcohol mutants", i.e. strains able to grow on benzoate or L-mandelate but not on benzyl alcohol, and "benzoate mutants", i.e. strains unable to grow on L-mandelate, benzyl alcohol or benzoate, were isolated. Three classes of mandelate mutants were obtained; those which lacked L-mandelate dehydrogenase; those which lacked benzoylforrnate decarboxylase; and those which lacked L-mandelate dehydrogenase, benzoylformate decarboxylase and the stable benzaldehyde dehydrogenase. The three benzyl alcohol mutants examined did not posses a functional benzyl alcohol dehydrogenase or labile benzaldehyde dehydrogenase. All the benzoate mutants studied were able to groxr on catechol but not on benzoate or its precursors. Mutants meso-constitutive for L-mandelate dehydrogenase and benzoylformate decarboxylase and hyperinducible for the stable benzaldehyde dehydrogenase were obtained as a result of spontaneous mutation and incubation with W-raethylilnitroso- / N-nitroguanidine. An examination of the growth patterns of the blocked mutants provided supporting evidence for the postulates of Kennedy and Kennedy & Fewson (1968 a, b) that the enzymes which convert L-mandelate, benzyl alcohol and their substituted analogues to the corresponding benzoates are nonspecific in their activity and indication; that L-mandelate is metabolised to benzoate only through benzoylforraate; and that 2-hydroxybenzoate is oxidised directly to catechol and not through benzoate. Heat denaturation experiments, the properties of the blocked mutants and the pattern of monovalent cation activation provided evidence for the existence of a heat-stable benzaldehyde dehydrogenase with a half-life of about 500min at 37

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: C A Fewson
• Keywords: Microbiology, Physiology
• Date of Award: 1970
• Depositing User: Enlighten Team
• Unique ID: glathesis:1970-73711
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jun 2019 08:56
• Last Modified: 14 Jun 2019 08:56
• URI: https://theses.gla.ac.uk/id/eprint/73711