Enhancement of glutamic-pyruvic transaminase activity in leptospirae by addition of rabbit serum.

Glutamic-pyruvic transaminase (GPT) in leptospirae was shown to have an optimal temperature of 30 C and pH 8.0. It was activated by cofactor pyridoxal phosphate, similar to GPT from other sources. However, GPT in all leptospirae, such as Leptospira canicola, L. icterohaemorrhagiae, L. autumnalis, and L. biflexa, evidently had less activity even when pyridoxal phosphate was present, in comparison with the cultivable spirochete Reiter treponeme and Streptococcus faecalis. The low level of activity of leptospiral GPT was enhanced more than 2.5-fold by the addition of about 10% rabbit serum, whereas GPT of S. faecalis did not show such enhancement. Enhancement of leptospiral GPT was greater with rabbit serum than with bovine or horse serum.