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)

An active form of phosphorylase phosphatase of Mr = 33,000, referred to as the catalytic subunit for over a decade, was purified to near-homogeneity from rabbit skeletal muscle. Repeated immunization of a sheep produced immunoglobulins that blocked the activity of the phosphatase. These immunoglobulins were affinity-purified on columns of immobilized phosphorylase phosphatase and used as macromolecular probes in a "Western" immunoblotting procedure with peroxidase-conjugated rabbit anti-sheep immunoglobulins. Only one protein, of Mr = 33,000, was stained in samples of the immunogen, attesting to the specificity of the probes. However, the Mr = 33,000 phosphatase protein was not detected in muscle extracts or in partially purified preparations. Instead, a single protein of Mr = 70,000 was detected. Limited proteolysis, in particular by Staphylococcus aureus V8 protease and thermolysin, converted the immunoreactive protein from Mr = 70,000 to Mr = 33,000. Coagulation of the phosphatase preparation with 80% ethanol at room temperature rendered the Mr = 70,000 protein insoluble, but allowed extraction of the Mr = 33,000 protein from the precipitate. Thus, we conclude that the immunoreactive protein of Mr = 70,000 is the "catalytic subunit" of phosphorylase phosphatase with a catalytic domain of Mr = 33,000. Previous purification schemes have yielded only the fragment of Mr = 33,000 due to its relative resistance to proteolysis and coagulation. Gel filtration chromatography of the "native" form of phosphorylase phosphatase showed Mr approximately 230,000. Both the Mr = 70,000 catalytic subunit and a Mr = 60,000 protein related to inhibitor-2 were detected by immunoblotting in the same fractions that exhibited activity after treatment with Co2+ and trypsin. Only the Mr = 60,000 protein was degraded during this activation process. We propose that the native phosphorylase phosphatase is an elongated structure with two-fold symmetry, containing one catalytic subunit of Mr = 70,000 and one regulatory subunit of Mr = 60,000.
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PMID:Phosphorylase phosphatase catalytic subunit. Evidence that the Mr = 33,000 enzyme fragment is derived from a native protein of Mr = 70,000. 298

Glycogen synthase (labelled in sites-3) and glycogen phosphorylase from rabbit skeletal muscle were used as substrates to investigate the nature of the protein phosphatases that act on these proteins in the glycogen and microsomal fractions of rat liver. Under the assay conditions employed, glycogen synthase phosphatase and phosphorylase phosphatase activities in both subcellular fractions could be inhibited 80-90% by inhibitor-1 or inhibitor-2, and the concentrations required for half-maximal inhibition were similar. Glycogen synthase phosphatase and phosphorylase phosphatase activities coeluted from Sephadex G-100 as broad peaks, stretching from the void volume to an apparent molecular mass of about 50 kDa. Incubation with trypsin decreased the apparent molecular mass of both activities to about 35 kDa, and decreased their I50 for inhibitors-1 and -2 in an identical manner. After tryptic digestion, the I50 values for inhibitors-1 and -2 were very similar to those of the catalytic subunit of protein phosphatase-1 from rabbit skeletal muscle. The glycogen and microsomal fractions of rat liver dephosphorylated the beta-subunit of phosphorylase kinase much faster than the alpha-subunit and dephosphorylation of the beta-subunit was prevented by the same concentrations of inhibitor-1 and inhibitor-2 that were required to inhibit the dephosphorylation of phosphorylase. The same experiments performed with the glycogen plus microsomal fraction from rabbit skeletal muscle revealed that the properties of glycogen synthase phosphatase and phosphorylase phosphatase were very similar to the corresponding activities in the hepatic glycogen fraction, except that the two activities coeluted as sharp peaks near the void volume of Sephadex G-100 (before tryptic digestion). Tryptic digestion of the hepatic glycogen and microsomal fractions increased phosphorylase phosphatase about threefold, but decreased glycogen synthase phosphatase activity. Similar results were obtained with the glycogen plus microsomal fraction from rabbit skeletal muscle or the glycogen-bound form of protein phosphatase-1 purified to homogeneity from the same tissue. Therefore the divergent effects of trypsin on glycogen synthase phosphatase and phosphorylase phosphatase activities are an intrinsic property of protein phosphatase-1. It is concluded that the major protein phosphatase in both the glycogen and microsomal fractions of rat liver is a form of protein phosphatase-1, and that this enzyme accounts for virtually all the glycogen synthase phosphatase and phosphorylase phosphatase activity associated with these subcellular fractions.
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PMID:The protein phosphatases involved in cellular regulation. Evidence that dephosphorylation of glycogen phosphorylase and glycogen synthase in the glycogen and microsomal fractions of rat liver are catalysed by the same enzyme: protein phosphatase-1. 300 40

Phosphorylase phosphatase purified from the protein-glycogen complex of rabbit muscle has a Mr of 34,000 by gel filtration and migrates as a single band of Mr 38,000 on sodium dodecyl sulfate gel electrophoresis, i.e., of the same size as the catalytic subunit of the sarcoplasmic complex of type 1 phosphatase (L. M. Ballou, D. L. Brautigan, and E. H. Fischer (1983) Biochemistry 22, 3393-3399). The enzyme, called PG-Ea, has a specific activity of 12,000 units/mg of protein and is essentially fully active, displaying at most a 20% further increase in activity on treatment with trypsin. As in the case of the catalytic subunit of the sarcoplasmic enzyme, tryptic attack decreases the size of PG-Ea to 33,000. PG-Ea is completely inhibited by the modulator protein (inhibitor 2) after formation of a complex of Mr 70,000. On incubation of this complex at 30 degrees C, the catalytic subunit is converted (t 1/2 = 30 min) to an inactive form (Ei) that can be reactivated by the protein kinase FA (J. R. Vandenheede, S.-D. Yang, J. Goris, and W. Merlevede (1980) J. Biol. Chem. 255, 11,768-11,774) or to a lower extent by trypsin-Mn2+. Also the trypsinized PG-Ea is inhibited by inhibitor 2, it forms with this a Mr 70,000 complex and undergoes an even faster (t 1/2 = 10 min) conversion to an Ei form that can be reactivated by the kinase FA or to a lower extent by trypsin-Mn2+. Enzymological comparison of PG-Ea and trypsinized PG-Ea with the FA-activated, isolated catalytic subunit of the sarcoplasmic phosphatase (called EaFA, E. Villa-Moruzzi, L. M. Ballou, and E. H. Fischer (1984) J. Biol. Chem. 259, 5857-5863) and with its trypsinized form shows several similarities. The most relevant of these is the very specific interaction with inhibitor 2, that takes to inactivation and allows the following reactivation by FA or by trypsin-Mn2+. However, the inactivation-reactivation patterns show also some differences, namely (i) the t 1/2 of the conversion to Ei is longer for PG-Ea than for EaFA, and (ii) the reactivation of PG-Ea and trypsinized PG-Ea with trypsin-Mn2+ is only partial. Altogether the similarity but not identity of PG-Ea and EaFA would suggest that they are either two different conformations of the same molecule or two isozymes.
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PMID:Purification and inactivation-reactivation of phosphorylase phosphatase from the protein-glycogen complex. 301 Aug 75

A 56,000-dalton protein with inherent phosphoprotein phosphatase activity was isolated from porcine brain capillaries. The enzyme is not activated by divalent metal ions but strongly inhibited by zinc ions. As phosphatase inhibitor 2 readily inhibits the enzymatic activity, the protein can be classified as a type I phosphatase. The protein is stable toward protease treatment. Limited digestion with trypsin does not convert the enzyme into an active form of lower molecular weight. The physical and enzymatical properties of the phosphatase exhibit considerable similarities to those of another 56,000-dalton phosphatase derived from rabbit reticulocytes.
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PMID:Isolation and partial characterization of a 56,000-dalton phosphoprotein phosphatase from the blood-brain barrier. 304 Sep 3

The complete primary structure of inhibitor-2, a specific inhibitor of protein phosphatase-1, has been determined. The protein consists of a single polypeptide chain of 203 residues, and has a relative molecular mass of 22835 Da. This molecular mass is significantly lower than earlier estimates based on sodium dodecyl sulphate polyacrylamide gel electrophoresis. The threonyl residue phosphorylated by glycogen synthase kinase-3 is located at position 72. The molecule is very hydrophilic, lacks cysteine residues and the single tryptophanyl and phenylalanyl residues are at positions 46 and 139, respectively. The N-terminal alanyl residue is N-acetylated. Digestion with Staphylococcus aureus V8 proteinase, trypsin, or cleavage with cyanogen bromide, destroyed the biological activity of inhibitor-2, demonstrating that many large fragments (e.g. 1-49, 49-92, 67-101, 108-134, 142-182 and 163-197) are inactive. Digestion with clostripain generated a peptide comprising residues 25-114 which retained 2% of the inhibitory potency of the parent molecule. There is no sequence homology between inhibitor-2 and inhibitor-1.
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PMID:The protein phosphatases involved in cellular regulation. Primary structure of inhibitor-2 from rabbit skeletal muscle. 351 70

Intact spermatozoa from goat cauda epididymides possess an ecto-(cyclic AMP-independent protein kinase) activity that causes transfer of the terminal phosphate of exogenously added [gamma-32P]ATP to the serine and threonine residues of several endogenous plasma-membrane phosphoproteins located on the external cell surface. Cyclic AMP, cyclic GMP, calmodulin and muscle cyclic AMP-dependent protein kinases I and II had no appreciable effect on the rate of phosphorylation of ecto-proteins by the intact cells. The ecto-enzyme is not derived from the catalytic subunit of a cyclic AMP-dependent kinase. Sperm ecto-kinase activity is not due to contamination of broken cells or any possible cell damage during incubation and isolation of spermatozoa. The phosphorylation reaction was linear for approx. 1 min and there was no detectable uptake of ATP by these cells. The activity of the ecto-kinase was strongly inhibited by proteinases and by the membrane-nonpenetrating surface probes. The products of the reaction were associated with the intact cells and the 32P of the labelled cells was largely lost when treated with Triton X-100 or proteinases: trypsin and pronase. These data are consistent with the view that the observed protein kinase and the phosphoproteins are located on the external surface of spermatozoa. Vigorously forward-motile whole spermatozoa showed a relatively high capacity to phosphorylate ecto-proteins that undergo rapid turnover. The results suggest the occurrence of a novel coupled-enzyme system (ecto-protein kinase and phosphoprotein phosphatase) on the sperm external surface that may modulate sperm physiology by determining the phosphorylated states of the ecto-proteins.
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PMID:Phosphorylation of external cell-surface proteins by an endogenous ecto-protein kinase of goat epididymal intact spermatozoa. 352 94

Cytosolic protein phosphotyrosine (PPT) phosphatase was measured using a new substrate, Tyr(32P)-labeled bovine serum albumin. Kidney was found as a particularly rich tissue source of PPT-phosphatase activity, containing twice as much as liver and over 10-fold more than brain, heart, lung, or skeletal muscle. An affinity column of Zn2+-iminodiacetate agarose adsorbed up to 60% of the PPT-phosphatase present in kidney extracts. Subsequent chromatography on DEAE-Sepharose separated the phosphatase into two peaks, labeled I and II, that had Mr = 34,000 and 37,000, respectively, upon gel filtration with Sephadex G-75 Superfine. Overall purification of 850- and 1100-fold was achieved with a net 4% yield. Both phosphatases hydrolyzed p-nitrophenylphosphate as well as the protein substrate in the presence of EDTA. Peak I phosphatase activity displayed a neutral pH optimum, had an absolute requirement for sulfhydryl compounds, and was sensitive to trypsin, whereas Peak II activity had an acidic pH optimum and was active without mercaptans. The two proteins also gave different fragmentation patterns by gel electrophoresis after digestion with S. aureus V8 protease. The results show that multiple forms of PPT phosphatase specifically interact with Zn2+ and provide a basis for further structural and functional comparisons among different members of the phosphoprotein phosphatase family.
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PMID:Cytosolic protein phosphotyrosine phosphatases from rabbit kidney. Purification of two distinct enzymes that bind to Zn2+-iminodiacetate agarose. 608 42

The 'native' Mg-ATP-dependent protein phosphatase was isolated from rabbit skeletal muscle by a procedure that avoided the use of organic solvents or heating at 90-100 degrees C. The purified enzyme was composed of two major proteins (molecular mass 37 kDa and 31 kDa) that were present in a 1:1 molar ratio, and accounted for 70-80% of the material. The 37-kDa component comigrated with the catalytic subunit of protein phosphatase-1, and its identity with this protein was established by peptide mapping, and by its cleavage to the characteristic 34-kDa and 33-kDa fragments following incubation with chymotrypsin. The 31-kDa protein comigrated with inhibitor-2, and its identity with this protein was established by its heat stability, ability to inhibit protein phosphatase-1 at nanomolar concentrations, and its phosphorylation on a threonine residue by glycogen synthase kinase 3. It is therefore concluded that the 'native' Mg-ATP-dependent protein phosphatase is composed of the catalytic subunit of protein phosphatase-1 (37 kDa) and inhibitor-2 (31 kDa) in a 1:1 molar ratio. The 'native' Mg-ATP-dependent protein phosphatase had virtually identical properties to the enzyme reconstituted from inhibitor-2 and the 37-kDa catalytic subunit of protein phosphatase-1. Each preparation had a similar specific activity and was inhibited by identical concentrations of inhibitor-1. Both enzymes could be activated by incubation with glycogen synthase kinase-3 and Mg-ATP, or by Mn2+ and trypsin (or chymotrypsin). However, Mn2+ alone, or proteinase digestion in the absence of Mn2+, failed to activate either preparation. Incubation with glycogen synthase kinase-3 and Mg-ATP did not dissociate the 'native' or 'reconstituted' enzymes, whereas treatment with Mn2+ and trypsin decreased their apparent molecular masses from 70 kDa to 35 kDa. Incubation with chymotrypsin converted the 'native' and 'reconstituted' enzymes to forms that required preincubation with glycogen synthase kinase-3, Mg-ATP and inhibitor-2, in order to exhibit catalytic activity. The Mg-ATP-dependent protein phosphatase reconstituted from the 'nicked' 33-kDa catalytic subunit dissociated upon activation, in contrast to the enzyme reconstituted from the undegraded 37-kDa catalytic subunit. The results suggest that a 3-4-kDa fragment at one end of the polypeptide is involved in strengthening interaction between the undegraded 37-kDa catalytic subunit and the phosphorylated form of inhibitor-2.
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PMID:The protein phosphatases involved in cellular regulation. Comparison of native and reconstituted Mg-ATP-dependent protein phosphatases from rabbit skeletal muscle. 609 83

Treatment of a pig heart phosphoprotein phosphatase (phosphoprotein phosphohydrolase, EC 3.1.3.16) of Mr 224 000 with 40% ethanol followed by gel-filtration on Sephadex G-150, dissociated the enzyme into an active component of Mr 31 000 and an inactive component of Mr 80 000. The inactive component reassociated with the active component, resulting in the formation of an enzyme form of Mr 123 000. A large excess of either component in the reassociation produced only this enzyme form. The ability of the inactive component to associate with the active component was lost by treatment of the inactive component with trypsin and heat (60 degrees C, 2 min) but not with DNAase and RNAase. Effects of the inactive component on the activities of the active component by the association were as followings. The inactive component: (1) stimulated slightly the 32P-H2B histone phosphatase activity in the presence of either NaCl or Mg(CH3COO)2 but inhibited strongly in the absence of the salts; (2) stimulated the 32P-H1 histone phosphatase activity in the presence of the salts; (3) inhibited the phosphorylase a phosphatase activity in the presence and absence of the salts; (4) enhanced the response to the stimulatory effects of the salts on the dephosphorylation of 32P-histone; and (5) protected the phosphorylase a phosphatase activity from inhibition by the salts.
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PMID:Isolation of an inactive component from pig heart phosphoprotein phosphatase and its reassociation with an active component. 624 55

Plasma membrane isolated from rat liver contained activities of phosphoprotein phosphatase dephosphorylating [32P]phosphorylase a or [32P]phosphohistone. The properties of the membrane-bound phosphatase were examined using these exogenous substrates. The optimal reaction rate was at pH near neutrality. At concentrations as low as 0.1-1.0 mM, Mg2+ or Mn2+ slightly stimulated the activity for phosphorylase a or phosphohistone, respectively; at higher concentrations, they were inhibitory with both substrates. Co2+ was inhibitory with both substrates, while Ca2+ had no significant effect. The phosphatase activities were inhibited by ATP, ADP, or AMP; the extents of inhibition were in opposite order with the two substrates. Phosphorylase phosphatase activity was strongly inhibited by KF or Pi. Phosphorylase phosphatase activity could be completely solubilized by incubating the membrane with 0.5 M NaCl or trypsin, and this was associated with several-fold activation. While Vmax values were increased, Km values for phosphorylase a were not much affected by these treatments. Unlike the soluble phosphatase, freezing in the presence of mercaptoethanol or by precipitation with ethanol failed to activate or to solubilize the membrane-bound phosphatase. The molecular weights of the NaCl-and the trypsin-solubilized phosphatase were estimated on gel filtration to be about 42,000 and 32,000, respectively. The present results indicate that the phosphoprotein phosphatase associated with liver plasma membrane shares several properties in common with phosphatases from other sources reported, and that, like those in the soluble fraction, it may be bound to some inhibitory proteins.
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PMID:Phosphoprotein phosphatase associated with rat liver plasma membrane. Properties of phosphorylase phosphatase and phosphohistone phosphatase. 627 67


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