DECARBOXYLATION AND SIDE TRANSAMINATION WHEN GLUTAMATE-DECARBOXYLASE FROM ESCHERICHIA-COLI ACTS ON SUBSTRATE-ANALOGS MODIFIED AT C-3 AND C-4

The interaction of glutamate decarboxylase with aspartate and glutamat e analogues modified at C-3 and C-4 was studied. 3-Arsonoalanine, 3-ph osphonoalanine, 2-amino-4-arsonobutyric acid, 2-amino-4-phospho-nobuty ric acid, a mixture of diastereoisomers of 4-(methylthio)glutamic acid , and erythro-4-(methylthio)glutamic acid were shown to be poor substr ates for the enzyme. Their decarboxylation was accompanied by transami nation of the coenzyme (PLP)(5) to pyridoxamine phosphate (PMP) which reversibly inactivated the enzyme. With arsonoalanine only part of the PLP was converted into PMP and another part irreversibly formed a com plex. 4-(Methylsulfonyl)-L-glutamic and 4-[(phenyl)(hydroxy)phosphoryl ]-L-glutamic acids did not react with the glutamate decarboxylase.