Intestinal lactase. Shift in intracellular processing to altered, inactive species in the adult rat.

摘要: The regulatory mechanism of decline in catalytic activity for intestinal lactase (lactase-phlorizin hydrolase, beta-galactosidase) as mammals mature has not been defined. Solubilized brush-border membranes from adult male rats (greater than 4 months age, 200-400 g) were examined by high performance liquid Zorbax GF-450 chromatography, subjected to denaturing acrylamide electrophoresis, blotted nitrocellulose, and identified specific polyvalent anti-lactase. Three major species present within the 235-kDa active peak (225, 130, 100 kDa). 100-kDa moiety was also prominent approximately 300-kDa region effluent, suggesting it is a catalytically inactive oligomer. In vivo synthesis assembly intraintestinal pulse [( 35S]methionine, 5 min) chase (15-120 revealed rapid (15 min chase; maximum, 60 intracellular endoplasmic reticulum-Golgi fraction multiple (64, 100, 175, 225 64-kDa disappeared membrane compartment transferred surface. 175-kDa appeared be processed 225-kDa unit prior relocation surface membrane. By 120 min, became predominant (approximately 60%) radiolabeled both brush border. rat, assembled molecular forms that are differentially processed: (a) degradation (64-kDa unit) or (b) transfer (225 130 kDa) (100 species. Although substantial proteins prevails, changes processing appear serve an important producing maturational activity. accompanying article (Castillo, R. O., Reisenauer, A. M., Kwong, L. K., Tsuboi, K. Quan, R., Gray, G. M. (1990) J. Biol. Chem. 265, 15889-15893) extends our studies during neonatal period maturation.