ISOLATION AND CHARACTERIZATION OF SALT-TOLERANT GLUTAMINASES FROM MARINE MICROCOCCUS-LUTEUS K-3

Marine Micrococcus luteus K-3 constitutively produced two salt-toleran t glutaminases, designated glutaminase I and II. Glutaminase I was hom ogeneously purified about approximately, 1620-fold with a 4% yield, an d was a dimer with a molecular weight of about 86,000. Glutaminase II was partially purified about 190-fold with a 0.04% yield. The molecula r weight of glutaminase II was also 86,000. Maximum activity of glutam inase I was observed at pH 8.0, 50 degrees C and 8-16% NaCl. The optim al pH and temperature of glutaminase II were 8.5 and 50 degrees C. The activity of glutaminase II was not affected by the presence of 8 to 1 6% NaCl. The presence of 10% NaCl enhanced thermal stability of glutam inase I. Both enzymes catalyzed the hydrolysis of L-glutamine, but not its hydroxylaminolysis. The K-m values for L-glutamine were 4.4 (glut aminase I) and 6.5 mM (glutaminase II). Neither of the glutaminases we re activated by the addition of 2 mM phosphate or 2 mM sulfate. p-Chlo romercuribenzoate (0.01mM) significantly inhibited glutaminase I, but not glutaminase II. The conserved sequences LA*V and V**GGT*A were ob served in the N-terminal amino acid sequences of glutaminase I, simila r to that for other glutaminases.