Previous methods for the measurement of
folylpolyglutamate synthetase have been modified and combined to facilitate assay of this
enzyme at the levels found in mammalian tissues. Batch adsorption of product onto
charcoal allowed the rapid analysis of multiple samples of partially purified
enzyme, e.g., column fractions. This technique, however, was unsuitable for the assay of
folylpolyglutamate synthetase in crude cytosols due to the presence of interfering
enzyme activities. On the other hand, the sequential use of
charcoal adsorption and batch elution from
DEAE-cellulose permitted isolation of the
folate product from assay mixtures containing crude
enzyme fractions. Under these conditions, interference from other
enzyme activities and background values were low enough for the quantitation of 10 pmol of oligoglutamyl
folate product.
Folylpolyglutamate synthetase was measured in a series of mouse tissues and
tumors.
Enzyme activity was quite low in all cases. Mouse liver and kidney and some of the
tumors studied had the highest levels (50-100 pmol product/h/mg
protein); other
tumors and spleen had lower levels.
Enzyme activity was at the limit of detection in intestine and lung and was below detection in brain, heart, and skeletal muscle.