OXIDATIVE-REDUCTIVE PATHWAYS FOR METABOLISM OF BIOGENIC ALDEHYDES

Abstract

This chapter describes oxidative–reductive pathways for metabolism of biogenic aldehydes. In brain and other tissues the aldehydes derived from the catecholamines, that is, the catecholaldehydes, may be either oxidized to the corresponding acid metabolites or reduced to the alcohol derivative. The β-hydroxy-substituted phenylethylamines are more readily reduced, after the initial deamination to produce the aldehyde, than the phenylethylamines which lack the β-hydroxyl group. These findings, coupled with some other observations have shown that norepinephrine and normetanephrine are metabolised primarily to the corresponding alcohol metabolites, whereas the major product of dopamine metabolism in the brain is the acid derivative. These metabolites are formed from the corresponding biogenic aldehyde intermediates by a reductive of oxidative pathway. Evidence has also been obtained which indicates that the NADPH-linked aldehyde reductase, alcohol:NADP oxidoreductase, but not the NADH-dependent enzyme, may be involved in the reduction of biogenic aldehydes including the catecholaldehydes in brain. In one study, it was observed that brain tissue from all classes of vertebrates possessed NADPH-linked aldehyde reductase, whereas, the tiger salamander and American chameleon were devoid of the NADH-linked aldehyde reductase activity.