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

1. Starved cells of a strain of Escherichia coli and its mutant uncA, treated with colicin K, E2 or E3, remained fully rescuable upon trypsin treatment (stage I in colicin action). The transition to stage II in colicin action (cells no longer rescuable by trypsin) was promoted by the addition of either glucose or D-lactate. 2. Aerobically glucose-grown cells of the normal strain were irreversibly killed by colicin K, E2 or E3 under anerobic conditions, while similarly treated cells ot its mutant uncA remained fully rescuable. The stage I-stage II transition in colicin action was blocked in normal cells under anaerobic conditions when succinate was the sole carbon source. 3. Arsenate alone had little effect on the progression of the stage I-stage II transition in normal cells, treated with colicin K. However, this transition was abolished in the presence of both arsenate and anaerobic conditions. 4. The initiation of colicin action could be coupled to the anaerobic electron transfer systems formate dehydrogenase-nitrate reductase and alpha-glycerophosphate dehydrogenase-fumarate reductase. 5. These results indicate that an energized state of the cytoplasmic membrane is required for the initiation of colicin action and that no high-energy phosphorylated compounds are necessary.
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PMID:Energy requirement for the initiation of colicin action in Escherichia coli. 109 62

All molybdenum enzymes except nitrogenase contain a common molybdenum cofactor, whose organic moiety is a novel pterin called molybdopterin (MPT). To assist in elucidating the biosynthetic pathway of MPT, two MPT-deficient mutants of Escherichia coli K-12 were isolated. They lacked activities of the molybdenum enzymes nitrate reductase and formate dehydrogenase, did not reconstitute apo nitrate reductase from a Neurospora crassa nit-1 strain, and did not yield form A, a derivative of MPT. By P1 mapping, these two mutations mapped to chlA and chlE, loci previously postulated but never definitely shown to be involved in MPT biosynthesis. The two new mutations are in different genetic complementation groups from previously isolated chlA and chlE mutations and have been designated as chlM and chlN (closely linked to chlA and chlE, respectively). The reported presence of Mo cofactor activity in the chlA1 strain is shown to be due to in vitro synthesis of MPT through complementation between a trypsin-sensitive macromolecule from the chlA1 strain and a low-molecular-weight compound from the nit-l strain.
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PMID:Involvement of chlA, E, M, and N loci in Escherichia coli molybdopterin biosynthesis. 294 96

A selenium-containing protein, selenoprotein A, is an essential component of the clostridial glycine reductase complex. This enzyme complex catalyzes the reductive deamination of glycine, which is coupled to the esterification of orthophosphate resulting in the formation of ATP. Sequence information was obtained by automated Edman degradation of peptides generated by digesting carboxamidomethylated selenoprotein A with chymotrypsin or trypsin or with endoproteinase Arg-C followed by Staphylococcus aureus V8 protease. The sequence near the selenocysteine (Sec) residue is -Cys-Phe-Val-Sec-Thr-Ala-Ala-Gly-Ala-Met-Asp-Leu-Glu-Asn-Glu-Lys-. Selenium-containing peptides isolated from digests of carboxamidomethylated selenoprotein A with trypsin or endoproteinase Arg-C were found to be blocked at the amino terminus. The sequence of the selenocysteine-containing peptide from selenoprotein A shows no homology with those of two other selenoproteins, glutathione peroxidase and formate dehydrogenase.
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PMID:Selenoprotein A of the clostridial glycine reductase complex: purification and amino acid sequence of the selenocysteine-containing peptide. 296 30

Affinity adsorbents based on immobilized triazine dyes offer important advantages circumventing many of the problems associated with biological ligands. The main drawback of dyes is their moderate selectivity for proteins. Rational attempts to tackle this problem are realized through the biomimetic dye concept according to which new dyes, the biomimetic dyes, are designed to mimic natural ligands. Biomimetic dyes are expected to exhibit increased affinity and purifying ability for the targeted proteins. Biocomputing offers a powerful approach to biomimetic ligand design. The successful exploitation of contemporary computational techniques in molecular design requires the knowledge of the three-dimensional structure of the target protein, or at least, the amino acid sequence of the target protein and the three-dimensional structure of a highly homologous protein. From such information one can then design, on a graphics workstation, the model of the protein and also a number of suitable synthetic ligands which mimic natural biological ligands of the protein. There are several examples of enzyme purifications (trypsin, urokinase, kallikrein, alkaline phosphatase, malate dehydrogenase, formate dehydrogenase, oxaloacetate decarboxylase and lactate dehydrogenase) where synthetic biomimetic dyes have been used successfully as affinity chromatography tools.
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PMID:Biomimetic dyes as affinity chromatography tools in enzyme purification. 1099 23

The 2',3'-dialdehyde derivative of ADP (oADP) has been shown to be an affinity label for the NAD+ binding site of recombinant Candida boidinii formate dehydrogenase (FDH). Inactivation of FDH by oADP at pH 7.6 followed biphasic pseudo first-order saturation kinetics. The rate of inactivation exhibited a nonlinear dependence on the concentration of oADP, which can be described by reversible binding of reagent to the enzyme (Kd = 0.46 mM for the fast phase, 0.45 mM for the slow phase) prior to the irreversible reaction, with maximum rate constants of 0.012 and 0.007 min-1 for the fast and slow phases, respectively. Inactivation of formate dehydrogenase by oADP resulted in the formation of an enzyme-oADP product, a process that was reversed after dialysis or after treatment with 2-mercaptoethanol (> 90% reactivation). The reactivation of the enzyme by 2-mercaptoethanol was prevented if the enzyme-oADP complex was previously reduced by NaBH4, suggesting that the reaction product was a stable Schiff's base. Protection from inactivation was afforded by nucleotides (NAD+, NADH and ADP) demonstrating the specificity of the reaction. When the enzyme was completely inactivated, approximately 1 mol of [14C]oADP per mol of subunit was incorporated. Cleavage of [14C]oADP-modified enzyme with trypsin and subsequent separation of peptides by RP-HPLC gave only one radioactive peak. Amino-acid sequencing of the radioactive tryptic peptide revealed the target site of oADP reaction to be Lys360. These results indicate that oADP inactivates FDH by specific reaction at the nucleotide binding site, with negative cooperativity between subunits accounting for the appearance of two phases of inactivation. Molecular modelling studies were used to create a model of C. boidinii FDH, based on the known structure of the Pseudomonas enzyme, using the MODELLER 4 program. The model confirmed that Lys360 is positioned at the NAD+-binding site. Site-directed mutagenesis was used in dissecting the structure and functional role of Lys360. The mutant Lys360-->Ala enzyme exhibited unchanged kcat and Km values for formate but showed reduced affinity for NAD+. The molecular model was used to help interpret these biochemical data concerning the Lys360-->Ala enzyme. The data are discussed in terms of engineering coenzyme specificity.
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PMID:Characterization of the NAD+ binding site of Candida boidinii formate dehydrogenase by affinity labelling and site-directed mutagenesis. 1105 19