Purification and some properties of L-glutamate decarboxylase from human brain.
Glutamate decarboxylase (EC 4.1.1.15) from human brain has been purified 8000-fold with respect to the initial homogenate. The molecular weight of the native enzyme was found to be 140000 by electrophoresis on a polyacrylamide gradient gel slab. The presence of a single protein band (Mr 67000) on sodium dodecylsulphate/polyacrylamide gel and the existence of only one N-terminal amino acid suggest that the enzyme consists of two similar if not identical polypeptide chains. The Km of the enzyme at the optimum pH of 6.8 is about 1.3 x 10(-3) M for glutamate and 0.13 x 10(-6) M for pyridoxal phosphate. The analysis of the effects of various inhibitors of mouse brain glutamate decarboxylase on the human enzyme confirms the strong competitive inhibition caused by 3-mercaptopropionic acid (Ki = 2.7 x 10(-6) M) while the Ki values for allylglycine and chloride ion are 1.8 x 10(-2) M and 2.2 x 10(-2) M, respectively.
D000596:Amino Acids / Q000032:analysis; D001921:Brain / Q000201:enzymology*; D002262:Carboxy-Lyases / Q000302:isolation & purification*; D005968:Glutamate Decarboxylase / Q000302:isolation & purification* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight
D000596:Amino Acids; D046911:Macromolecular Substances; D002262:Carboxy-Lyases; D005968:Glutamate Decarboxylase