STUDIES ON AMINO ACID RACEMASES .2. PURIFICATION AND PROPERTIES OF GLUTAMATE RACEMASE FROM LACTOBACILLUS-FERMENTI

A purification procedure has been developed for the glutamate racemase (EC 5.1.1.3) from Lactobacillus fermenti (ATCC 9338) which results in preparations purified 2000-fold with respect to a cell extract. The enzyme is stabilized by the presence of mercaptoethanol and other sulfhydryl containing compounds. The molecular weight of the enzyme has been estimated to be 23 000 by chromatography on Sephadex G-150. Kinetic studies indicate a Km for d-glutamic acid of 2.2 mM and that hydroxylamine, riboflavin, FMN, FAD, and certain structural analogues of FAD are inhibitors of the racemase catalyzed reaction. The enzyme appears to be extremely specific for glutamic acid since aspartic acid, alanine, α-aminobutyric acid, or α-methylglutamic acid are completely inactive either as substrates or inhibitors. © 1969.