UDP-GALACTOSE-4-EPIMERASE ACTIVITY OF DEVELOPING MOUSE BRAIN AND LIVER EXTRACTS

UDP-galactose-4-epimerase from acetone powder extracts of developing mouse brain and liver exhibited significant variation as a function of age. Acetone powders were prepared from pooled brains and pooled livers of Swiss albino mice of one through 64 days of age. Aqueous buffered extracts from these powders were assayed enzymatically for epimerase activity, and total nitrogen was determined by a micro-Kjeldahl procedure to measure enzyme specific activities. In the brain, epimerase specific activity reaches a maximum between 8 and 16 days post-partum. This peak of total activity is also observed at 16 days post-partum, and it coincides with myelination. It also coincides with the active incorporation of galactose and serine in brain gangliosides and neutral glycolipids as reported earlier by Burton et al. By contrast, the peak of epimerase specific activity which appears at between 4 and 8 days for liver is not reflected in the total enzyme activity measurement, thus showing that liver epimerase activity remains essentially constant as specific activity to wet weight during mouse development. These data are consistent with a possible enzyme control mechanism which affects galactose metabolism and incorporation in the brain of the mouse. © 1969.