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Aromatic alcohol oxidase: A new membrane‐bound H 2 O 2 ‐generating enzyme in alimentary tissues of the slug Arion ater

1989; Wiley; Volume: 251; Issue: 3 Linguagem: Inglês

10.1002/jez.1402510302

1097-010X

Vincent M. Mann, Andrew T. Large, Sultan M Khan, Zulfiqar Ali Malik, Martin Connock,

Insect and Pesticide Research

Abstract We employed a sensitive spectrophotometric technique to detect H 2 O 2 ‐generating enzymic activities capable of utilizing aldehydes or alcohols as substrates. We analysed tissue homogenates and subcellular fractions of the terrestrial slug Arion ater . Of the tissues tested, those of the alimentary system (especially crop and digestive gland) had the greatest activity and generated H 2 O 2 when supplied with a variety of alcohol and aldehyde substrates. Aldehyde oxidase activity was soluble and had high apparent affinity for benzaldehyde. This activity is probably analogous to mammalian aldox (aldehyde oxidase; E.C.1.2.3.1), since it could use an artificial electron acceptor system and greatly preferred benzaldehyde to hypoxanthine. However, it differed from guinea pig liver aldehyde oxidase in that salicylaldehyde was a potent inhibitor rather than a substrate. Alcohol oxidase activity was particulate but not localised in mitochondria or peroxisomes. In digestive gland, it was localised differently from mannitol oxidase. In crop, the subcellular sites are either the same or inseparable by isopycnic density gradient centrifugation in sucrose gradients. Activity was at least ten times greater with aromatic alcohols than with ethanol, propanol, or butanol. No activity was detected with methanol, and the enzyme could not utilise an artificial electron acceptor system or pyridine nucleotides. Aromatic alcohol oxidase differed from mannitol oxidase with respect to temperature and pH sensitivity and in exhibiting greater apparent affinity for its substrates. The alcohol oxidase accepted a wide variety of aromatic alcohols as substrates. In several respects it resembled the corresponding enzyme of wood‐rot fungi, implying that the slug utilises dietary lignin or lignin precursors. Possible dietary, microbicidal, and detoxifying roles are considered for slug aldehyde and alcohol oxidases.