Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To study the sorting of proteins in Dictyostelium discoideum, we used vector constructs that contain cDNA coding for the entire beta-hexosaminidase protein to prepare transformants of a mutant that lacks this enzyme activity. These transformants overexpressed active, normally processed beta-hexosaminidase. The overexpressed enzyme colocalized with other acid hydrolases in the soluble fraction of vesicles in the lysosomal region of Percoll gradients. The sorting of other hydrolases was unaltered. We also prepared transformants with constructs that contain 22 (Hex 22-Inv), 70 (Hex 70-Inv), and 532 (Hex 532-Inv) amino-terminal amino acids from beta-hexosaminidase fused in frame with the coding sequence for the yeast SUC2 gene product, invertase. Fusion molecular masses were those expected for fully N-glycosylated proteins. Hex 22-Inv was rapidly (t1/2 less than 30 min) and quantitatively secreted. The others were slowly (t1/2 greater than 5 h) and partially secreted. Each expressed invertase activity. During growth, the invertase activity of Hex 70-Inv and Hex 532-Inv was retained to the same extent as that of endogenous lysosomal enzymes. Most of the Hex 70-Inv migrated in Percoll gradients with vesicles of intermediate density (d = 1.055), but a portion co-migrated with lysosomal enzymes at d = 1.08. Hex 70-Inv was sulfated, and its N-glycosides were resistant to endoglycosidase H, indicating Golgi processing. Hex 70-Inv and Hex 532-Inv, like endogenous lysosomal enzymes, were subject to developmentally induced secretion.
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PMID:A sequence in beta-hexosaminidase from Dictyostelium discoideum required for sorting of proteins to a compartment involved in developmentally induced secretion. 153 76

Gp80, a cell-adhesion molecule in Dictyostelium discoideum, is modified by N- and O-linked oligosaccharides, and a glycosylphosphatidylinositol (GPI) anchor. To identify sequences important for the addition of these modifications to gp80, we created a hybrid protein in which the C-terminal 136 amino acids of yeast invertase were replaced by the C-terminal 110 amino acids of gp80. When expressed in D. discoideum, this protein (Inv-gp80) was not GPI-anchored and was retained in a pre-Golgi compartment. Inv-gp80 did, however, display characteristics of a transmembrane protein, suggesting a novel mechanism for its retention. We also expressed a truncated version of the hybrid protein in which the C-terminal 22 amino acids of the Inv-gp80 were deleted. The truncated protein (Inv-gp80stop) was O-glycosylated and secreted. These observations indicate that the hybrid protein is not abnormally folded and demonstrate the importance of the C-terminal 22 amino acids in the retention of Inv-gp80. Together, the data suggest that oligomerization of the protein blocks its GPI anchoring.
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PMID:Lack of glycosyl-phosphatidylinositol anchoring leads to precursor retention by a unique mechanism in Dictyostelium discoideum. 770 55