An alternative route from α-oxoglutarate to succinyl-CoA as part of the tricarboxylic acid cycle. Rather than going through the α-oxoglutarate dehydrogenase reaction, ¿-oxoglutarate condenses with NH₃ to form α-iminoglutarate, then is reduced to glutamic acid, decarboxylated to γ-aminobutyrate (GABA), transaminated to succinic semialdehyde and oxidised to succinyl-CoA.