gamma-Glutamyltranspeptidase from Proteus mirabilis: localization and activation by phospholipids.

Antiserum was prepared against the purified gamma-glutamyltranspeptidase (EC 2.3.2.2) of Proteus mirabilis. The antiserum inactivated the gamma-glutamyltranspeptidase activities of both purified enzyme and intact cells. Native cells were agglutinated with the antibody. Immunocytochemical studies with indirect immunofluorescence and electron microscopy analysis suggested that gamma-glutamyltranspeptidase is localized on the surface of the cell. Its distribution in the cell wall or periplasmic space or both was also confirmed by the treatment of cells with lysozyme-EDTA. The purified enzyme was activated by the addition of membrane phospholipids isolated from the same bacterium. The hydrolysis activity was stimulated more than the transpeptidation activity by several phospholipids.