Comparative kinetics of azathioprine and metazathioprine mercaptolysis in presence of physiological thiols.

Kinetic parameters of mercaptolysis of azathioprine (AZA) and metazathioprine (MAZA) to 6-mercaptopurine in phosphate buffer, pH 7.4, under the influence of physiological thiols (glutathione and cysteine) at 25 degrees, 30 degrees and 37 degrees C were determined and compared. It comes out that the mercaptolysis of MAZA is significantly faster under the influence of both mentioned thiols if compared to that reaction of AZA. Furthermore, the mercaptolysis of MAZA and AZA proceeded significantly faster under the influence of cysteine than on the glutathione heterolysis.