Figure 1.

Subcellular compartmentation of GABA metabolism.Enzymes are shown in blue letters, with biochemically characterized enzymes indicated by bold lettering. Dashed arrows and question marks indicate enzymes and transporters which have not been studied. The dotted line with a red bar represents negative regulation. Abbreviations: ABAL, 4-aminobutanal; ADC, arginine decarboxylase; ALDH, aldehyde dehydrogenase; Agm, agmatine; AIH, agmatine iminohydrolase; ALMT, aluminum-acticated malate transporter; Arg, arginine; CT, cationic amino acid transporter; N-Carbamoyl-Put, N-Carbamoylputrescine; CPAH, N-Carbamoylputrescine amidohydrolase; CuAO, copper amine oxidase; GABA, 4-aminobutyrate; GAD, glutamate decarboxylase; GABP, GABA permease; GABA-T, GABA transaminase; GAT, GABA transporter; GHB, 4-hydroxybutyrate; GLYR, glyoxylate/succinic semialdehyde reductase; PAO, polyamine oxidase; ProT, proline transporter; Put, putrescine; SSA, succinate semialdehyde; SSADH, succinate semialdehyde dehydrogenase; Spd, spermidine; Spm, spermine; TCA, tricarboxylic acid (adapted from refs. 4, 11 and 20).