Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

The properties of purified mammalian adenosine 3':5'-cyclic monophosphate (cAMP)- and guanosine 3':5'-cyclic monophosphate (cGMP)-dependent protein kinases were compared. Several physical characteristics of the two enzymes were similar, including size, shape, affinity for cyclic nucleotide binding, and K(m) for ATP. In addition, the amino acid composition of the two proteins indicated a close composition homology (70-90%). Both cyclic nucleotide-dependent protein kinases catalyzed phosphorylation of rat liver pyruvate kinase (EC 2.7.1.40) and fructose 1,6-diphosphatase (EC 3.1.3.11), rabbit skeletal muscle glycogen synthase (EC 2.4.1.11) and phosphorylase b kinase (EC 2.7.1.38), and calf thymus histone H(2)b. The phosphorylation of several synthetic peptides and of trypsin-sensitive and trypsin-insensitive sites in glycogen synthase suggested similar recognition sites on the protein substrates for the two kinases. The cAMP-dependent protein kinase was the better catalyst with each protein or peptides substrate. The results suggest that the two enzymes evolved from a common ancestral protein.
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PMID:Adenosine 3':5'-cyclic monophosphate- and guanosine 3':5'-cyclic monophosphate-dependent protein kinases: possible homologous proteins. 19 77

Six new defective pyruvate kinase variants have been characterized in patients suffering from chronic hemolysis. Partially purified enzyme variants exhibited various anomalies from immunological, kinetic, stability and electrophoretic points of view. The significance of the electrophoretic anomalies has been interpreted in view of the normal post-synthetic maturation of the precursor enzyme L'4 into L2L'2 and L4, and the ability of trypsin to induce in vitro the transition L'4 leads to L4 has been tested. One defective enzyme existed in a single L'4 form and could not be transformed by trypsin into L4. In three cases slow-moving L'4 and L2L'2 forms were transformed by trypsin into an abnormal slow-moving L4 form. In the last two observations the L'4 and L2L'2 forms exhibited normal mobility and were normally transformed by trypsin into L4. The relevance of these data to the functional anomalies of the defective variants and to the nature of the primary genetic anomaly giving rise to the congenital defects in erythrocyte pyruvate kinase is discussed.
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PMID:Significance of the electrophoretic modifications of defective pyruvate kinase variants. Study of six new observations. 43

The functional changes, associated with the sequential transformation of L'4 into L4 pyruvate kinase (ATP:pyruvate 2-O-phosphotransferase, EC 2.7.1.40) were studied. L'4 enzyme from human erythrocytes shows strong hysteretic behaviour: the initial rate of the enzyme preincubated with an unsaturating concentration of phosphoenolpyruvate is much higher than of the enzyme preincubated with ADP, at the same phosphoenolpyruvate concentration, although the "final activity" (the activity of the linear part of the reaction progress curve) was the same in both cases. This phenomenon was observed both in the presence and absence of fructose 1,6-diphosphate. High concentrations of both Mg2+free and MgATP2- diminish the difference in initial rate, between the ADP and phosphoenolpyruvate preincubated enzymes: Mg2+free by stabilizing the phosphoenolpyruvate-induced form; ATPMg2- by stabilizing the ADP-induced form. The magnitude of the difference in initial rates of the ADP-or phosphoenolpyruvate-preincubated enzyme is a function of both substrates. L4 pyruvate kinase (either from human liver or trypsin treated L'4 enzyme) does not, or to a very slight extent, show such behaviour. L'2L2 pyruvate kinase shows behaviour intermediate between L'4 and L4 enzymes. A model is proposed to describe the kinetic behaviour of L'4 and L4 enzymes.
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PMID:Functional changes associated with the sequential transformation of L'4 into L4 pyruvate kinase. 49 28

Pyruvate kinase (ATP: pyruvate 2-O-phosphotransferase, EC 2.7.1.40) from human liver and red cells has been purified to homogeneity; its subunit structure and some of its kinetic characteristics have been studied. The influence of a partial proteolysis by trypsin on the subunit structure, the isozymic pattern and the kinetic characteristics of red cell and liver enzyme have been investigated. From the results of this study we may conclude that: 1. Liver (L-type) pyruvate kinase is composed of 4 identical L subunits while the major form of erythrocyte enzyme (PK-R2) is a heterotetramer designated as L2L2', the molecular weight of L' being slightly higher than that of L subunits (63 000 and 58 000 respectively). Pyruvate kinase PK-R1, predominant in the erythroblasts and the young red cells, is composed of four identical L' subunits. 2. A mild tryptic attack is able to transform PK-R1 into PK-R2, then PK-R2 into pyruvate kinase L (PK-L). The same proteolytic treatment transforms the L' subunits into L ones. 3. Consequently L-type pyruvate kinase seems to be initially synthesized in the erythroid precursors as an L4' enzyme secondarily partially proteolysed into L2L2'. In liver a very active proteolytic system would be responsible for the total transformation into L4 pyruvate kinase. 4. L4' enzyme exhibits Michaelis-Menten kinetic behaviour with an apparent Michaelis constant of 3.8 mM whereas L4 enzyme shows both positive and negative homotropic interactions towards phosphoenolpyruvate and has [S] 0.5 of 1.2 mM. The characteristics of L2L2' are roughly intermediate between those of L4' and of L4. Fructose 1,6-biphosphate decreases [S]0.5 for these three pyruvate kinase forms without suppressing the differences in the apparent affinity for phosphoenolpyruvate of these enzymes. 5. L4 pyruvate kinase is more inhibited by Mg-ATP than L4', with L2L2' in the intermediate range. 6. Tryptic treatment of each enzyme form studied transforms its kinetic behaviour into that observed for L4.
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PMID:The genetic system of the L-type pyruvate kinase forms in man. Subunit structure, interrelation and kinetic characteristics of the pyruvate kinase enzymes from erythrocytes and liver. 62 93

The hydrophobic nature of proteins is characterized by a degree of 2-p-toluidinonaphthalene-6-sulphonate (TNS) affinity to them and is pronounced quantitatively in the semi-saturated (C1/2) concentrations. This index correlates directly with the position of TNS emission maximum after the binding with proteins and reversely with the yield of fluorescence. The preparations of phosphofructokinase, lactate dehydrogenase, xantinoxidase, glyceratekinase, lysozyme, RNase during the long (1-2 h) contact with TNS change the values C1/2, that evidences for interaction with the hydrophobic indicator of new structures of protein molecule or for a change in the nature of its linkage itself. An attempt is made to characterize the accessible for TNS hydrophobic nature of individual proteins by a coefficient of molar hydrophobic nature which unites three mentioned characteristics. Serum albumin, insulin, glucogon, alpha chemotrypsin, DNase are most hydrophobic, pyruvate kinase, aldolase, urease, RNase--least hydrophobic, Glycerate kinase, pyruvate decarboxylase, phosphofructokinase, lactate dehydrogenase, alcohol dehydrogenase, xanthinoxidase, trypsin, lysozyme are in intermediate position.
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PMID:[Comparative characteristics of hydrophobic nature of certain proteins by their interaction with 2-p-toluidinonaphthalene-6-sulfonates]. 120 4

Thioltransferase, an enzyme which catalyzes the thiol/disulfide exchange reaction in the presence of GSH, was purified to homogeneity on 15% SDS-PAGE from human (36,000-fold purification) and bovine (23,000-fold) erythrocyte hemolysates. These enzymes had similar properties in their monomeric structures (M(r) = 11,000) and broad specificities for substrates ranging from low-molecular disulfides (S-sulfocysteine, cystamine, and cystine) to protein disulfides (trypsin and insulin). They were highly sensitive to SH-reagents (monoiodoacetic acid and mercuric chloride), but were protected from inactivation by the presence of disulfides (GSSG, cystamine, and cystine). Phosphofructokinase and pyruvate kinase that had been inactivated by disulfides were reactivated effectively by the addition of thioltransferase with GSH. In addition, disulfides in membrane proteins of human erythrocytes that have been oxidatively damaged by diamide treatment were reduced to the SH-free form more effectively by incubation with thioltransferase.
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PMID:Study on human erythrocyte thioltransferase: comparative characterization with bovine enzyme and its physiological role under oxidative stress. 163 68

The ornithine decarboxylase-inducing factor (ODC factor) was purified about 1,000-fold in 42% yield from the ascites fluids of an Ehrlich ascites tumor by a combination of centrifugation and concanavalin A (ConA) treatment. A single ip injection of 0.5 micrograms of the purified factor per mouse resulted in half-maximum induction of liver ODC. The factor was found to be a trypsin- and chymotrypsin-resistant, acidic glycoprotein (pI about 4.43) with a minimum molecular weight of about 70 kilodaltons, containing a disulfide bond(s) in its functional domain. It did not react with ConA. This factor induced retrodifferentiation of liver function, causing a marked increase of prototype M2 isozyme of pyruvate kinase. It reduced liver catalase activity, and also modified thyroid hormone metabolism, reducing the serum levels of T4 and T3. These results suggest that the ODC factor is multifunctional and induces many of the changes observed in a tumor-bearing host.
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PMID:Purification of ornithine decarboxylase-inducing factor from cell-free ascites fluid of Ehrlich ascites tumor and its characteristics. 170 56

The affinity label 8-[(4-bromo-2,3-dioxobutyl)thio]adenosine 5'-triphosphate (8-BDB-TA-5'-TP) reacts covalently with rabbit muscle pyruvate kinase, incorporating 2 mol of reagent/mol of enzyme subunit upon complete inactivation. Protection against inactivation is provided by phosphoenolpyruvate, K+, and Mn2+ and only 1 mol of reagent/mol of subunit is incorporated [DeCamp, D.L., Lim, S., & Colman, R.F. (1988) Biochemistry 27, 7651-7658]. We have now identified the resultant modified residues. After reaction with 8-BDB-TA-5'-TP at pH 7.0, modified enzyme was incubated with [3H]NaBH4 to reduce the carbonyl groups of enzyme-bound 8-BDB-TA-5'-TP and to introduce a radioactive tracer into the modified residues. Following carboxymethylation and digestion with trypsin, the radioactive peptides were separated on a phenylboronate agarose column followed by reverse-phase high-performance liquid chromatography in 0.1% trifluoroacetic acid with an acetonitrile gradient. Gas-phase sequencing gave the cysteine-modified peptides Asn162-Ile-Cys-Lys165 and Cys151-Asp-Glu-Asn-Ile-Leu-Trp-Leu-Asp-Tyr-Lys161, with a smaller amount of Asn43-Thr-Gly-Ile-Ile-Cys-Thr-Ile-Gly-Pro-Ala-Ser-Arg55. Reaction in the presence of the protectants phosphoenolpyruvate, K+, and Mn2+ yielded Asn-Ile-Cys-Lys as the only labeled peptide, indicating that inactivation is caused by modification of Cys151 and Cys48.
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PMID:Cysteinyl peptides of rabbit muscle pyruvate kinase labeled by the affinity label 8-[(4-bromo-2,3-dioxobutyl)thio]adenosine 5'-triphosphate. 233 78

A new reactive fluorescent ADP analog has been synthesized: 2-[(4-bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 5'-diphosphate (2-BDB-T epsilon A-5'-DP). Rabbit muscle pyruvate kinase is inactivated by 200 microM 2-BDB-T epsilon A-5'-DP in a biphasic manner, with an initial loss of 75% activity followed by a slow total inactivation. The rate constants for both phases exhibit nonlinear dependence on reagent concentration, consistent with reversible formation of an enzyme-reagent complex (KI = 133 microM) prior to irreversible reaction. Loss of activity is prevented by substrates. The best protection against inactivation is provided by phosphoenolpyruvate (PEP), KCl, and MnSO4, suggesting that the reaction occurs in the region of the PEP binding site. Incorporation of 1.7 mol/mol enzyme subunit accompanies 90% inactivation by 200 microM 2-BDB-T epsilon A-5'-DP in 80 min. However, in the presence of PEP, KCl, and MnSO4, 1.0 mol of reagent is incorporated when the enzyme is only 14% inactivated. These results indicate that 2-BDB-T epsilon A-5'-DP reacts with two groups on the enzyme, one of which is at or near the PEP binding site. Incubation of pyruvate kinase with related nucleotide analogs lacking a 5'-diphosphate or a diketo group suggests that the diketo group, but not the diphosphate, is essential for inactivation. The enolized form of the bromodioxobutyl group resembles phosphoenolpyruvate and probably directs the reagent to the PEP binding site. Modified enzyme, prepared by incubating pyruvate kinase with 200 microM 2-BDB-T epsilon A-5'-DP in the absence and presence of phosphoenolpyruvate, KCl, and MnSO4, was reduced with [3H]NaBH4, carboxymethylated, and digested with trypsin. Nucleotidyl peptides were isolated by chromatography on phenylboronateagarose followed by reverse phase high pressure liquid chromatography. Two radioactive peptides were identified: Asn162-Ile-Cys-Lys165 and Ile141-Thr-Leu-Asp-Asn-Ala-Tyr-Met-Glu-Lys150. Only the tetrapeptide was modified in the presence of PEP, KCl, and Mn+ when the enzyme retained most of its activity. Cys164 is thus designated the nonessential modified residue, while modification of Tyr147 near the active site of pyruvate kinase is responsible for loss of enzymatic activity. The observed biphasic kinetics of inactivation are due to the negatively cooperative reaction of 2-BDB-T epsilon A-5'-DP with Tyr147 in the tetramer. The new compound, 2-BDB-T epsilon A-5'-DP, may have general application as an affinity label of ADP and PEP sites in other proteins.
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PMID:2-[(4-Bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 5'-diphosphate. A new fluorescent affinity label of a tyrosyl residue in the active site of rabbit muscle pyruvate kinase. 248 27

The effect of substrate phosphorylation on the susceptibility to proteolytic cleavage by trypsin-like enzymes was investigated using the model heptapeptide Leu-Arg-Arg-Ala-Ser-Leu-Gly, a peptide representing the endogenous phosphorylation site of pyruvate kinase. Phosphorylation of Ser 5 altered the kinetics of proteolysis by two proteases, trypsin and rat plasma kallikrein, both of which cleaved between Arg 3 and Ala 4. In the case of trypsin, phosphorylation decreased the rate of cleavage 47-fold. In the case of rat plasma kallikrein, phosphorylation decreased proteolysis 13-fold. Phosphorylation resulted in an apparent redirection of the preferential site from Arg 3 to Arg 2. Because sequences analogous to this model peptide are commonly found in exposed domains of globular proteins, and since these regions are susceptible to both phosphorylation and protease attack, the results indicate that substrate phosphorylation may selectively influence protein processing and turnover.
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PMID:Substrate phosphorylation can inhibit proteolysis by trypsin-like enzymes. 275 4


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