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)

In the large granule fraction of rat liver, the density distribution of inhibitor-sensitive neutral ribonuclease is similar to that for acid hydrolases and its density distribution is similarly modified by Triton WR-1339 accumulation in lysosomes. Particulate neutral ribonuclease is latent; the enzyme is unmasked by very low digitonin concentrations or hypoosmotic shock. These observations demonstrate that the bulk of liver neutral ribonuclease is associated with the lysosomal system. In view of the neutral pH optimum of the enzyme and of some particularities of its distribution in fractionation experiments, the possiblilty of an extrahepatic origin of neutral ribonuclease has been investigated. After partial pancreatectomy, a significant decrease is observed in both plasma and liver neutral ribonuclease. The effect is specific, for it does not occur for other lysosomal enzymes. Also, labelled bovine pancreatic ribonuclease, when injected intravenously, is taken up by the liver. The sedimentable labelled enzyme has a density distribution similar to the distribution of other foreign proteins, horseradish peroxidase or yeast invertase. These results are explained by the uptake of plasmatic neutral ribonuclease from pancreatic origin by the liver.
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PMID:Hepatic nucleases. Extrahepatic origin and association of neutral liver ribonuclease with lysosomes. 0 Dec 73

Full-value diets of similar composition were given to male rats weighing 207-230 g, by intravenous (group 1) or intragastric (group 2) routes. The proportion of amino acids, fats and carbohydrates was 9.9:15.7:74.4 (with regard to their calorific value). The diet calorific value comprised 60.6 kcal/rat/day. An average mass increase in group 1 was 2.44 +/- 0.14 g/day, in group 2 - 1.75 +/- 0.11 g/day. The protein content and activities of alpha- and gamma-amylase, invertase, maltase, and glycil-L-leucine dipeptidase were assayed in the intestinal mucosa of the proximal portion of the small intestine in group 1 rats, while a decreased alpha-amylase activity in the distal portion of the small intestine was recorded in the animals of group 2. The mass of the pancreas in the rats of group 1 and 2 was authentically lower than in the control rats which received oral feeding with natural foods. The lowest mass of the pancreas was observed in the rats of group 1. Specific activity of trypsin, lipase and RNase in the pancreatic tissues of rats in groups 1 and 2 was similar. The results of the study have evidenced a lowered function of the digestive system under conditions of artificial feeding, especially in case of intravenous nutrition.
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PMID:[Digestive function of the small intestine and pancreas in rats on artificial feeding]. 309 Jul 82

Two glycopeptide hydrolases, an endo-beta-N-acetylglucosaminidase and peptide:N-glycanase (amidase), have been isolated from defatted jack bean meal by standard procedures involving differential solubility and column chromatography. The purified products appear to be free of contaminating proteases and exoglycosidases, and their substrate specificity has been explored with regard to both glycan and peptide structure of the substrates. The endoglycosidase appears to be specific for high mannose glycans; no hydrolysis of either hybrid or complex glycans has been observed. It shows limited activity with two intact glycoproteins, ribonuclease B and yeast invertase, and gives optimal rate with glycopeptides. Free glycan-Asn derivatives are poor substrates in comparison with glycopeptides or glycan-Asn derivatives where the alpha-amino group has been dansylated. The amidase will liberate both high mannose, hybrid, and asialo-complex glycans from both proteins and peptides, but many glycans in intact proteins or in long peptides are resistant to the amidase and become active as substrates only after further proteolytic cleavage. The best substrates appear to be those with the glycosylated asparagine no more than 4-5 residues in from either the NH2- or COOH-terminal end of the peptide. Sialylated glycans do not appear to be released by the amidase.
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PMID:Purification and characterization of two glycopeptide hydrolases from jack beans. 333 94

Peptide N-glycosidase from Flavobacterium meningosepticum cleaves complex as well as neutral glycoproteins (Plummer, T.H., Jr., Elder, J.H., Alexander, S., Phelan, A.W., and Tarentino, A.L. (1984) J. Biol. Chem. 259, 10700-10704). Examples of neutral glycoprotein substrates include ribonuclease B (one high mannose oligosaccharide chain) and yeast external invertase (nine chains/invertase subunit). The rate of deglycosylation by the glycosidase was greatly enhanced if the glycoprotein substrate was denatured prior to enzyme treatment, from a low of 11-fold for external invertase to a high of 844-fold for ribonuclease B. Peptide N-glycosidase F was unable to cleave the asparaginyl-N-acetylglucosamine bond in endo-beta-N-acetylglucosaminidase H-modified external invertase or ribonuclease B, although that in similarly modified glycopeptide substrate was cleaved. Ribonuclease B was digested sequentially with various exoglycosidases to produce an oligosaccharide chain of varied length. Using the resulting forms of ribonuclease B as substrates for peptide N-glycosidase F, the minimum oligosaccharide chain for cleavage was the di-N-acetyl-chitobiosyl core unit.
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PMID:Requirements of cleavage of high mannose oligosaccharides in glycoproteins by peptide N-glycosidase F. 394 Oct 69

1. Homogenates of the mucosa of the small intestine of the guinea pig were separated by fractional sedimentation into seven different fractions. The enzymic properties of some of these subcellular fractions were compared with those obtained from the mucosa of the small intestine of the rabbit and cat. 2. The enzymic properties of the low-speed sediment (15000g-min.) were investigated and it was shown that invertase and alkaline ribonuclease were predominantly located in this subcellular fraction, whereas alkaline phosphatase, aryl-amidase, acid phosphatase, acid ribonuclease and phosphoprotein phosphatase, though true constituents of this fraction, occurred to varying degrees in other subcellular structures also. 3. It was shown that the most probable source of the enzymic activities observed in the low-speed sediment was the brush border. Electron micrographs of the purified brush-border fraction indicated vesicles derived from the brush-border membrane. 4. A method is described for the fractionation of mucosal homogenates into a brush border-plus-nuclei fraction, a mitochondrial fraction, a microsomal fraction and a particle-free supernatant. The fractions were shown to be relatively pure, as indicated by the distribution of invertase, DNA, succinate dehydrogenase, glucose 6-phosphatase and 6-phosphogluconate dehydrogenase. 5. Most of the activity of four lysosomal enzymes present in the nuclei-free homogenate was sedimented at 375000g-min., suggesting the occurrence of lysosomal particles in mucosal homogenates. 6. Further fractionation of the microsomal membranes into three fractions is described. The enzymic composition of the membrane fractions is given and discussed in relation to their structure as seen in electron micrographs.
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PMID:Studies on the fractionation of mucosal homogenates from the small intestine. 428 74

Even though most of the hepatic binding capacity for mannose-terminated glycoproteins has previously been shown to reside in the hepatocytes (not in the non-parenchymal cells), detailed evidence for the specific uptake of mannose-terminated ligands has been lacking. In the present studies, yeast invertase, a large glycoprotein (Mr 270 000) containing about 50% mannose, was shown to be taken up into hepatocytes by receptor-mediated endocytosis. The uptake was saturable and could be specifically inhibited by mannosides or by a Ca2+ chelator. The asialo-glycoprotein receptor was not involved. The low-Mr (13 000) ligand ribonuclease B, which contains a single high-mannose glycan, was not taken up by hepatocytes; however, it was taken up as fast as invertase by non-parenchymal liver cells. After injection of 131I-invertase into a rat in vivo, about one-half of the labelled protein was recovered in the hepatocytes. On a per-cell basis, each endothelial cell contained 3-4 times as much radioactivity as did the hepatocytes. On fractionation of hepatocytes in sucrose gradients, invertase showed a different intracellular distribution from that of asialo-fetuin, in that invertase moved much faster into that region of the gradient where the lysosomes were recovered. This indicates that invertase and asialo-fetuin are not transported intracellularly by identical mechanisms.
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PMID:Uptake of mannose-terminated glycoproteins in isolated rat liver cells. Evidence for receptor-mediated endocytosis in hepatocytes. 649 38

We studied the uptake of D-glucose and L-tryptophan by the small intestine and estimated the activities of the intestinal brush border enzymes (sucrase, lactase, NA+-K+-ATPase and alkaline phosphatase) and lysosomal enzymes in rats receiving T-2 toxin orally. considerable decrease occurred in glucose and tryptophan uptake and in brush border sucrase, lactase and (Na+-K+)-ATPase. Alkaline phosphatase activity and release of lysosomal enzymes (acid phosphatase and acid ribonuclease) was unchanged.
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PMID:Effects of T-2 toxin on glucose and tryptophan uptake and intestinal mucosal enzymes. 671 77

Mannose-specific binding sites for horseradish peroxidase (HRP) were studied in fixed sections of various tissues by a method reported previously. Liver sinusoidal cells, mast cells of lymph nodes, and alveolar macrophages of the lung and skin fibroblasts were main cell types showing mannose-specific binding of HRP. Macrophages, fibroblasts, and mast cells in the connective tissue of other organs also showed the reaction. However, macrophages of the spleen, and cultured 3T3 cells and L-cells did not give the reaction. The specificities of the binding reaction were studied by determining the approximate concentrations of competing sugars that suppressed the specific binding of HRP. It was found that the endogenous lectins in macrophages, fibroblasts, mast cells, and liver sinusoidal cells showed similar specificities toward various carbohydrates. D-Mannose and L-fucose had the highest affinity toward the lectins (competing ability for the binding of HRP). D-Mannose-6-phosphate, N-acetyl-D-glucosamine, D-glucose, D-ribose, and D-arabinose showed intermediate affinity, whereas D-xylose and D-galactose showed low affinity. Polymerized mannose in mannan and glycoproteins rich in mannose groups (invertase and ribonuclease B) showed much higher affinity to the binding sites than free mannose.
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PMID:Mannose-specific binding sites for horseradish peroxidase in various cells of the rat. 683 41

Lactase-phlorizin hydrolase (LPH) and sucrase-isomaltase (SI) are intestine-specific microvillus membrane hydrolases whose specific activities demonstrate reciprocal regulation during development but whose mechanisms of regulation have not been fully defined. To investigate transcriptional control of these two proteins, the rat LPH and SI genes were cloned, and antisense probes for preprocessed mRNAs (pre-mRNAs) were developed from intron sequence. LPH mRNA, as measured by quantitative ribonuclease (RNase) protection assays, was abundant before weaning and decreased two- to fourfold during weaning, whereas SI mRNA was first detected 14 days after birth and increased rapidly to abundant levels by age 28 days. LPH and SI pre-mRNA levels paralleled those of their respective mRNAs. LPH transcriptional rate declined during weaning, whereas that of SI increased during this time as determined by RNase protection assays of pre-mRNAs and nuclear run-on assays. In the adult rat, LPH mRNA was restricted to the jejunum and proximal ileum, whereas SI mRNA was detected throughout the small intestine, a pattern regulated by transcriptional rate as confirmed by nuclear run-on assays. Lactase and sucrase specific activities correlated well with their respective protein and mRNA concentrations in all experiments. We conclude that gene transcription plays a major role in the developmental and horizontal regulation of LPH and SI biosynthesis and that these two genes are regulated differently in rat small intestine.
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PMID:Transcriptional regulation of intestinal hydrolase biosynthesis during postnatal development in rats. 794 23

The enzyme that catalyzed the conversion of human salivary alpha-amylase family A (HSA-A) to family B (HSA-B) was identified. It was partially purified from the precipitate obtained by centrifugation of human saliva at 105,000 x g for 60 min by solubilization with 3[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate and column chromatographies with Sephacryl S-300-HR and hydroxylapatite. The enzyme preparation was practically free from contaminating exoglycosidases and proteases. The enzyme cleaved the N,N'-diacetylchitobiose moiety of the sugar chain of HSA-A, as shown by the isolation of the protein moiety which contained 1 GlcNAc and 1 Fuc residue and the sugar chain (Gal)2(Fuc)1(GlcNAc)2(Man)3(GlcNAc). This enzyme also cleaved the N,N'-diacetylchitobiose moiety of the sugar chain of human transferrin tetraglycopeptide Asn-Tyr-Asn(GlcNAc)2(Man)3(GlcNAc)2(Gal)2-Lys to yield equimolar amounts of peptide Asn-Tyr-Asn(GlcNAc)Lys and sugar chain (Gal)2(GlcNAc)2(Man)3(GlcNAc). The enzyme was identified as an endo-beta-N-acetylglucosaminidase. The enzyme acted on HSA-A with desialylated and defucosylated outer chain moieties of the sugar chains at a similar rate as that of native HSA-A. The enzyme activity was reduced to 13 and 5% using HSA-A with the sugar chains whose outer chain moieties lacked Gal and GlcNAc, respectively, from the nonreducing end. The enzyme also acted on human transferrin, calf fetuin, and asparagine oligosaccharides of transferrin and fetuin. On the other hand, the enzyme did not act on ovalbumin, RNase B, Taka-amylase, yeast invertase, and ovalbumin asparagine oligosaccharides. These results indicate that human salivary endo-beta-N-acetylglucosaminidase is specific for complex type sugar chains and can release the sugar chains from native glycoproteins and glycopeptides regardless of the existence of a Fuc residue on the proximal GlcNAc of the N,N'-diacetylchitobiose core of their sugar chains. The source of the enzyme was epithelial cells peeling from the oral cavity epithelium into saliva. The enzyme was thought to be integrated on the surface of the epithelial cell membrane. This enzyme was named endo-beta-N-acetylglucosaminidase HS. Thus, these studies indicate that the properties of the enzyme are distinct from those of known endo-beta-N-acetylglucosaminidase and endo-beta-N-acetylglucosaminidase HS is a novel endo-beta-N-acetylglucosaminidase.
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PMID:Human salivary endo-beta-N-acetylglucosaminidase HS specific for complex type sugar chains of glycoproteins. 834 Apr 28


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