Mutual interaction in unsaturated fat oxidase system

Bannatyne, William Reid (1961) Mutual interaction in unsaturated fat oxidase system. PhD thesis, University of Glasgow.

Abstract

One of the main problems involved in studies of the nature and action of the unsaturated-fat oxidase, lipoxidase, has been the similarity of the lipoxidase reaction to haematin-catalysed oxidation of unsaturated fats. While it would be comparatively easy to distinguish between the action of haematin-free lipoxidase and lipoxidase-free haematin with existing methods, crude plant extracts contain mixtures of the two systems and may give rise to confusion. The characteristics of such mixtures can only be adequately studied if haematin-free lipoxidase is available, and while purified haematins can be fairly readily prepared, the isolation of lipoxidase presents major difficulties. This thesis reports the examination of a number of methods of purification and describes the subsequent separation of a highly active, haematin-free lipoxidase from soya-beans. The fractionation procedure involves precipitation of the enzyme at its isoelectric point with ammonium sulphate. The characteristics of the haematin-free lipoxidase system are defined using a method of assay which depends on the spectrophotometric measurement of the diene conjugation developed in sodium linoleate by the enzymic action. By means of a slight modification of the lipoxidase assay, the unsaturated-fat oxidase behaviour of the haematin compounds is also examined. The would described in this thesis includes a study of lipoxidase-haematin interaction. The effect of haematin on lipoxidase behaviour is examined, using the direct spectrophotometric assay system with respect to such variables as pH, reaction time, linoleate concentration, haematin concentration and lipoxideise concentration. Rapid breakdown of the haematin molecule in the lipoxidase reaction system ira described and the influence of haematin decomposition on diene conjugation in the adopted system is discussed. Aided by these studies, attention is given to the unsaturated fat oxidase behaviour of crude soya extracts. The characteristics of soya extracts and of lipoxidase haematin mixtures are examined and compared using the diene conjugation method of assay. Arising from the data obtained, it is concluded that in unsaturated-fat oxidations catalysed by crude plant extracts, possible interference from haematins cannot be overlooked.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: John Hawthorn
• Keywords: Physiology
• Date of Award: 1961
• Depositing User: Enlighten Team
• Unique ID: glathesis:1961-73147
• 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/73147