Some properties of gamma-glutamyl transpeptidase from Fusobacterium nucleatum

A series of chromatographic techniques was used to purify gamma-glutamyl transpeptidase from Fusobacterium nucleatum ATCC 23726. The purified enzyme was homogenous with a molecular weight (MW) of approximately 101 kD consisting of two different subunits with MW of 67 kD and 31 kD. Its distribution by treatment of lysozyme-EDTA suggested that the enzyme was a periplasmic protein. The pl of the enzyme was 5.9 to 6.2, and the optimum pH of the transpeptidation and the hydrolytic reaction was 8.0. Glycylglycine, glycine and methionine were good acceptors, and the enzyme reaction, in the presence of glycylglycine, was especially efficient. Glutamic acid, glutamine and serine were poor acceptors, and the enzyme activity was inhibited by these amino acids. The apparent Km value for the gamma-glutamyl donor (gamma-glutamyl-p-nitroanilide) was 4.9 x 10(-4)M and that for the acceptor (glycylglycine) was 0.19 M. Affinity-labelling reagents, such as DON, azaserine and AT-125 strongly inhibited the enzyme activity, and its activity was inhibited by L-serine plus borate, as is mammalian gamma-glutamyl transpeptidase. The antibodies against gamma-glutamyl transpeptidase from bovine kidney reduced the activity of the bacterial enzyme by 65%. These results indicate that the catalytic sites in F. nucleatum gamma-glutamyl transpeptidase were similar to those in mammalian gamma-glutamyl transpeptidase.