GHB degradation via TCA cycle is the major metabolic route in Arabidopsis thaliana

Abstract

Gamma-hydroxybutyric acid (GHB) is a product of the reduction reaction of chemically reactive succinic semi-aldehyde (SSA), which itself is produced from the degradation of GABA. It is regarded as a short-chain fatty acid. Despite our understanding of the synthesis of GHB, little is known about its fate. Exogenous application of 0.1 mM GHB to pop2 x ssadh, a double mutant incapable of catabolizing GABA, increased the endogenous GHB level by 13-fold compared to the wild type. The GHB dynamic studies by feeding and relieving from treatments showed that GHB is rapidly metabolized in wild-type plants compared to the pop2 x ssadh double mutant. Although regarded as a short-chain fatty acid, GHB level was not altered in mutants of the beta oxidation (β-oxidation) pathway following exogenous feeding. Therefore, the metabolism back to SSA, and then the TCA cycle appears to be the major route for GHB degradation. However, the presence of another catabolic route such as secondary modifications cannot be ruled out.