Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A soluble lectin which agglutinates trypsin-treated rabbit erythrocytes was purified from calf heart using affinity chromatography on asialofetuin-Sepharose. Its molecular weight was determined by gel filtration to be approximately 17,000. On polyacrylamide gel electrophoresis in sodium dodecyl sulfate, the predominant molecular species had a molecular weight of 9,000, suggesting that the lectin is a dimer. Binding studies performed with iodinated lectin revealed that neuraminidase-treated calf erythrocytes contained approximately 5 X 10(6) lectin binding sites per cell. Native calf and rabbit erythrocytes bound the lectin, but human and rat erythrocytes required neuraminidase and trypsin treatment, respectively, for lectin binding to occur. A number of saccharides, glycopeptides, and glycoproteins possess haptene inhibitory activity toward lectin binding to erythrocytes. The most potent of these have either galactose beta leads to galactose beta leads to, galactose beta N-acetylglucosamine beta leads to, or galactose beta leads to N-acetylglucosamine beta leads to sequences at their nonreducing termini. Lactose and galactose beta 1 leads to 3N-acetylgalactosamine are the next best haptenes. Finally, alpha-linked galactose residues and free galactose are very weak haptenes. The presences of a terminal sialic acid residue impairs haptene activity in all instances. Calf heart also contains a membrane-associated lectin which is very similar but not identical with the soluble lectin. A soluble beta-galactoside binding lectin was also isolated from calf lung. It has the same molecular size and subunit structure as the soluble heart lectin and is antigenically identical. In binding studies, the pattern of inhibition by various haptenes was the same for all three lectins.
 ...
PMID:Isolation and properties of beta-galactoside binding lectins of calf heart and lung. 82 31

The amino acid sequence of thiogalactoside transacetylase, a dimer, has been determined. The monomer contains 202 amino acid residues in a single polypeptide chain and has a molecular weight of 22,671. The analysis was carried out by treatment of the carboxymethylated protein with cyanogen bromide and with trypsin. All seven cyanogen bromide peptides were isolated in pure form and were ordered by peptides isolated from tryptic digests. The sequence analysis was aided by determination of the DNA sequence of the lacA gene. The amino terminus of the protein is heterogenous because the initiator methionine is only partially cleaved. Another rather unusual feature of this cytoplasmic protein is a very hydrophobic segment in the center portion of the chain. Comparison of the amino acid sequence of thiogalactoside transacetylase to those of the lac repressor, beta-galactosidase, and lactose permease did not reveal any marked similarities. Therefore, there is no obvious evolutionary relatedness among proteins of the Lactose Operon.
 ...
PMID:The amino acid sequence of thiogalactoside transacetylase of Escherichia coli. 392 33

Galactosyltransferase and UDP-[3H]galactose are commonly used to identify O-linked N-acetylglucosamine (O-GlcNAc)-bearing proteins and peptides. In this report we show that immobilized Ricinus communis agglutinin I (RCA I) specifically binds in vitro galactosylated O-GlcNAc-bearing peptides, facilitating their selective isolation from complex mixtures. First, the peptide YSDSPSTST was O-GlcNAc glycosylated, galactosylated, and sialylated. Of these three glycoforms, only the one with a terminal galactose interacted with the lectin. Next, RCA I was used to isolate glycopeptides from the O-GlcNAc-bearing basic phosphoprotein (BPP) of human cytomegalovirus. BPP was overexpressed using baculovirus, [3H]galactosylated, digested with trypsin, and fractionated on RCA I. Peptides that were not galactosylated passed through the column, whereas the majority of the radiolabeled glycopeptides interacted weakly with the lectin and did not require lactose or elution. These radiolabeled peptides eluted as a broad peak with the leading edge being characterized by more hydrophobic glycopeptides and the lagging edge by less hydrophobic peptides, suggesting that the polypeptide backbone may influence the interaction with the lectin. Lactose was required to elute the remaining radiolabeled peptides, suggesting that these peptides are multiply glycosylated. The weakly interacting glycopeptides were analyzed directly by liquid chromatography/electrospray-mass spectrometry (LC/ES-MS). Glycopeptides corresponding to both of the major sites of glycosylation of BPP were identified. Thus, RCA I greatly facilitates the selective isolation of in vitro galactosylated O-GlcNAc glycopeptides from complex mixtures and substantially reduces the purification required for subsequent site-mapping by gas-phase sequencing and/or LC/ES-MS.
 ...
PMID:Specific isolation of O-linked N-acetylglucosamine glycopeptides from complex mixtures. 857 67

Ricin is a glycosylated proteinous toxin that is registered as toxic substance by Chemical Weapons convention. Current detection methods can result in false negatives and/or positives, and their criteria are not based on the identification of the protein amino acid sequences. In this study, lactose-immobilized monolithic silica extraction followed by tryptic digestion and liquid chromatography/mass spectrometry (LC/MS) was developed as a method for rapid and accurate determination of ricin. Lactose, which was immobilized on monolithic silica, was used as a capture ligand for ricin extraction from the sample solution, and the silica was supported in a disk-packed spin column. Recovery of ricin was more than 40%. After extraction, the extract was digested with trypsin and analyzed by LC/MS. The accurate masses of molecular ions and MS/MS spectra of the separated peptide peaks were measured by Fourier transform-MS and linear iontrap-MS, respectively. Six peptides, which were derived from the ricin A-(m/z 537.8, 448.8 and 586.8) and B-chains (m/z 701.3, 647.8 and 616.8), were chosen as marker peptides for the identification of ricin. Among these marker peptides, two peptides were ricin-specific. This method was applied to the determination of ricin from crude samples. The monolithic silica extraction removed most contaminant peaks from the total ion chromatogram of the sample, and the six marker peptides were clearly detected by LC/MS. It takes about 5 h for detection and identification of more than 8 ng/ml of ricin through the whole handling, and this procedure will be able to deal with the terrorism using chemical weapon.
 ...
PMID:Determination of ricin by nano liquid chromatography/mass spectrometry after extraction using lactose-immobilized monolithic silica spin column. 2183 21