Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.108 (lactase)
 2,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biosynthesis and maturation of the human intestinal lactase-phlorizin hydrolase (LPH; EC 3.2.1.23-3.2.1.62) has been studied in cultured intestinal biopsies and mucosal explants. Short time pulse labelling revealed on high mannose intermediate of Mr 215,000 which was converted upon endo-beta-N-acetylglucosaminidase H (endo-H) digestion to a polypeptide of Mr 200,000. The brush border form of LPH was revealed after longer pulse periods and has Mr 160,000. It possesses mainly complex oligosaccharide chains and, owing to its partial endo-H sensitivity, at least one chain of the high mannose type. Leupeptin partially inhibited the appearance of the Mr-160,000 polypeptide. Monensin treatment of biopsies resulted in the modification of the Mr-160,000 species to the Mr-140,000 molecule, which was endo-H sensitive. Pulse-chase analysis indicated a slow post-translational processing of the high mannose precursor (Mr 215,000) to yield the mature brush-border form (Mr 160,000) of LPH. Our results further indicate that LPH is synthesized as a single polypeptide precursor which is intracellularly cleaved to yield the mature brush border of LPH. The data presented suggest that this cleavage occurs during the translocation of the molecule across the Golgi complex.
 ...
PMID:Biosynthesis and maturation of lactase-phlorizin hydrolase in the human small intestinal epithelial cells. 310 75

The proteolytic processing of rabbit intestinal lactase-phlorizin-hydrolase (LPH) was studied by pulse-chase and continuous labeling experiments in organ culture from 15-day-old rabbits in the presence of glycosylation and processing inhibitors. Monensin and brefeldin A inhibited the two proteolytic cleavages of the precursor indicating that they are post-Golgi events as previously reported for the unique cleavage of LPH in man. The inhibition was not related to a concomitant alteration glycosylation; in fact, if trimming was blocked by MDNM the abnormal glycosylated precursor was proteolytically processed normally. Finally the use of the anti-microtubular drug colchicine strongly inhibited both cleavages and caused accumulation of the complex-glycosylated precursor form the brush border fraction indicating that proteolytic events depend on intact microtubule (transport).
 ...
PMID:Analysis of lactase processing in rabbit. 826 50