Capillary electrophoresis of methotrexate polyglutamates and its application in evaluation of gamma-glutamyl hydrolase activity

Abstract

A rapid and sensitive procedure for the separation of methotrexate (MTX) polyglutamates2 using capillary electrophoresis (CE) is described as it applies to the in vitro assay of the enzyme gamma-glutamyl hydrolase (GGH, EC 3.4.22.12). Distinct separation of MTX and polyglutamylated forms (up to glu4) is achieved within 10 min using a 75 microns I.D. capillary (50 cm, +25 kV), and enables quantitation of both reactant and enzyme products. As activity can be reliably determined using less than 5 x 10(5) eukaryotic cells, this new technique can be used to measure GGH in patient tumor samples and investigate the relationship between GGH levels and clinical MTX resistance.