Improved assays of alpha-lactalbumin and galactosyltransferase

The development and evaluation of a method for the determination of galactosyltransferase and alpha-lactalbumin activities using the addition of Dowex resin to the sample to separate substrate from products are described. For both assays galactosyltransferase activity was optimized by the addition of detergent, and relevant control incubations were included. The assay conditions were optimized for epididymal tissue and standards, and the assays were validated for accuracy and specificity with authentic bovine proteins and lactating rat mammary gland homogenates. Galactosyltransferase and alpha-lactalbumin activities in tissues were dependent on the extraction procedure used. Epididymal and testicular homogenates reduced the slopes of internal standards of galactosyltransferase but only testicular homogenates depressed slopes of internal standards of alpha-lactalbumin, necessitating the use of internal standards in the validation of the assays.