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The alpha ‐oxidation system of brain microsomes. Cofactors for alpha ‐hydroxy acid decarboxylation
Author(s) -
MacDonald Robert C.,
Mead James F.
Publication year - 1968
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02531201
Subject(s) - decarboxylation , chemistry , cofactor , oxidative decarboxylation , microsome , substrate (aquarium) , oxidase test , biochemistry , enzyme , stereochemistry , carbanion , organic chemistry , catalysis , biology , ecology
Abstract A one‐carbon degradation of long‐chain fatty acids, which was found to occur in the brains of rats in vivo, has been investigated in a brain microsomal fraction in vitro. Decarboxylation of the α‐hydroxy acid, a possible intermediate product between the substrate and the next shorter acid, in the presence of brain microsomal fraction was enhanced by ATP, NAD, and a dialyzable fraction from the supernatant fraction. The cofactor requirement for the decarboxylation of the α‐hydroxy acids provided by the dialyzable fraction can be met by several reducing agents or ferrous ion. The effectiveness of several possible cofactors for the decarboxylation of α‐hydroxy acids has been evaluated. It is concluded that the decarboxylation of the α‐hydroxystearic acid may be a reaction with molecular oxygen catalyzed by an oxidase or oxygenase that requires iron in the reduced state for activity. The possibility that the reaction proceeds through an α‐keto acid intermediate has been examined in the light of new knowledge of the conditions for decarboxylation. It is concluded that a short‐lived keto acid is a possible intermediate. Definitive proof however is lacking because the characteristics of the reaction require that such an intermediate decarboxylate without dissociating from the enzyme.