ANALYSIS OF LACTASE PROCESSING IN RABBIT

The proteolytic processing of rabbit intestinal lactase-phlorizin-hydr olase (LPH) was studied by pulse-chase and continuous labeling experim ents in organ culture from 15-day-old rabbits in the presence of glyco sylation and processing inhibitors. Monensin and brefeldin A inhibited the two proteolytic cleavages of the precursor indicating that they a re post-Golgi events as previously reported for the unique cleavage of LPH in man [1]. The inhibition was not related to a concomitant alter ation glycosylation; in fact, if trimming was blocked by MDNM the abno rmal glycosylated precursor was proteolytically processed normally. Fi nally the use of the anti-microtubular drug colchicine strongly inhibi ted both cleavages and caused accumulation of the complex-glycosylated precursor form in the brush border fraction indicating that proteolyt ic events depend on intact microtubule (transport).