Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
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A low molecular weight protein found in the soluble extract of bovine adrenal medulla, and having a high affinity for calcium ions has been purified to apparent homogeneity. The purification requires three steps, including ammonium sulfate fractionation, ion exchange chromatography on DEAE-cellulose, and gel filtration on Sephadex G-100. The protein was homogeneous by the criteria of both standard and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, sedimentation velocity analysis, and NH2-terminal analysis. The calcium-binding protein is very acidic and has an isoelectric point of 4.27. Aspartic and glutamic acid together account for 30% of the total amino acid composition. The ultraviolet absorption spectrum reveals a A280/A260 ratio of 0.83 and shows discrete maxima at 258, 264, 269, 278, and 284 nm. Two moles of calcium are bound per mole of protein. The apparent Kp is approximately 20 muM. The molecular weight was found to be 16,000 +/- 1,000 by both sodium dodecyl sulfate gel electrophoresis and sedimentation equilibrium ultracentrifugation. The protein was found to consist of a single polypeptide chain by the criteria of tryptic peptide mapping and NH2-terminal analysis. Amino acid analysis revealed the absence of tryptophan, single residues of cysteine and histidine, and 2 residues of tyrosine. The protein was void of carbohydrate and phosphate. The structural similarities and possible functional correlation between adrenal medulla calcium-binding protein and troponin-C from muscle tissue are discussed.
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PMID:Purification and characterization of a troponin-C-like protein from bovine adrenal medulla. 81 60

The presence of a single cysteine in the sweet-tasting protein monellin was confirmed by titrations with p-hydroxymercuribenzoate (PHMB) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB). The sulfhydryl group in native monellin reacts very slowly with each of these reagents, indicating that the sulfhydryl is relatively inaccessible. In the presence of either 6 M guanidine-HCl, 8 M urea, or 1% sodium dodecyl sulfate, the rate of reaction of the sulfhydryl group with titrant is dramatically increased. Under a variety of conditions, the presence of 1 mole of sulfhydryl per mole of protein (of molecular weight 10,700) was found. Reaction of the sulfhydryl by titration with PHMB or DTNB leads to loss of sweetness. The free sulfhydryl is also lost by carboxymethylation of monellin in the presence of guanidine-HCl, yielding a protein that is not sweet. Exposure to air in the presence of denaturant leads to a decrease in the sweetness of monellin. Sweetness of the PHMB-reacted monellin can be recovered upon treatment of the protein with mercaptoethanol, and the partial loss of sweetness that occurs with air exposure is lessened in the presence of mercaptoethanol. It is postulated that alteration of the single sulfhydryl group of monellin leads to a change in the tertiary structure of the protein and hence its sweet taste.
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PMID:The sulfhydryl group of monellin: its chemical reactivity and importance to the sweet taste. 96 95

Beta-cyano-L-alanine synthase [L-cysteine hydrogen-sulfide-lyase (adding HCN), EC 4.4.1.9] was purified about 4000-fold from blue lupine seedlings. The enzyme was homoegeneous on gel electrophoresis and free of contamination by other pyridoxal-P-dependent lyases. The enzyme has a molecular weight of 52,000 and contains 1 mole of pyridoxal-P per mole of protein; its isoelectric point is situated at pH 4.7. Its absorption spectrum has two maxima, at 280 and 410 nm. L-Cysteine is the natural primary (amino acid) substrate; beta-chloro- and beta-thiocyano can serve (with considerably lower affinity) instead of cyanide as cosubstrates for cyanoalanine synthase. The synthase is refractory to DL-cycloserine and D-penicillamine, potent inhibitors of many pyridoxal-P-dependent enzymes. Cyanoalanine synthase catalyzes slow isotopic alpha-H exchange in cysteine and in end-product amino acids; the rates of alpha-H exchange in nonreacted (excess) cysteine are markedly increased in the presence of an adequate cosubstrate; no exchange is observed of H atoms in beta-position.
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PMID:Beta-cyanoalanine synthase: purification and characterization. 105 33

A naturally occurring monodisperse Cu-thionein was prepared using ammonium sulfate precipitation followed by ion exchange (DEAE 23) and gel chromatography (Sephadex G-75). The chromatographic steps were repeated at least twice, or until the Cu-thionein remained homogeneous when subjected to analytical polyacrylamide disc electrophoresis. The molecular weight of this copper protein was 9500+/-500. Up to 24.3% cysteine residues were determined, indicating the relationship to the metallothioneins. Aromatic amino acids were virtually absent, while there were about three times as many acidic amino acid residues, including aspartate and glutamate, as in metallothioneins. 10 g atoms of Cu were measured per mole of protein. The copper binding strength of thionein was extremely high. Displacement by protons (pH 1.5) and gel chromatography or dialysis employing EDTA were not effective. Dialysis against diethyldithiocarbamate produced a protein essentially free of copper. Both the ultraviolet properties and the circular dichroism measurements proved identical with those properties reported for artificially prepared Cu-thionein (see ref.[1]. The major absorption was in the far ultraviolet region with a weak shoulder at 270 nm attributable to copper charge-transfer transititions. 6 Cotton extrema were seen at 213, 283 and 302 nm (negative) and 245, 328 and 359 nm (positive). The possible role of Cu-thionein as an electron transport system was discussed.
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PMID:A naturally occurring Cu-thionein in Saccharomyces cerevisiae. 110 11

50-S ribosomal subunits from the extreme halophilic bacterium, Halobacterium cutirubrum, contain an alanine-rich acidic "A" protein which resembles the L7--L12 multimer (Kaltschmidt and Wittmann, 1970) found in the 50-S ribosomal subunit of Escherichia coli cells. The protein contains 24 mole % alanine and is devoid of histidine, tryptophan and cysteine. Unlike E. coli which has two forms of the "A" protein distinguished solely by the acetylation state of the serine amino terminus. H. cutirubrum 50-S subunits contain only one unsubstituted form of the "A" protein in vivo. However, during purification of ribosomes from cells grown between 25 and 37 degrees C the latter "A" protein undergoes rapid, specific, in vitro enzymatic alteration at its carboxy-terminal end. When the halophile is grown in the temperature range of 40 to 42 degrees C the cleaving enzyme is not active and only one form of the "A" protein is found on the ribosomes.
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PMID:Temperature related alterations in the acidic alanine-rich "A" protein from the 50S ribosomal particle of the extreme halophile, Halobacterium cutirubrum. 110 49

Cysteine synthase [O-Acetyl-L-serine acetate-lyase (adding hydrogen-sulfide) EC 4.2.99.8] has been highly purified from the extract of rape, Brassica chinensis var. Komatsuna. The purified preparation appeared to be homogeneous on Sephadex G-100 gel filtration and dodecylsulfate-polyacrylamide gel electrophoresis, showing a molecular weight of about 62,000. The latter method also suggested that this enzyme was composed of two identical subunits. The enzyme contained 2 moles of pyridoxal phosphate per mole of enzyme.
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PMID:Cysteine synthase from rape leaves. 115 55

Pyridoxal phosphate N-oxide and 2'-hydroxypyridoxal phosphate served as the coenzyme for aspartate beta-decarboxylase (EC 4.1.1.12) from Pseudomonas dacunhae. Reconstituted enzymes with those pyridoxal phosphate analogues exhibited an absorption band near 370 nm. Close to 1 mole of vitamin B6 derivative is bound per minimal catalytic unit with high affinity. The decarboxylase, desulfinase, and transaminase activites of the both pyridoxal phosphate derivate-enzymes are relatively low. But the Km values for aspartate and cysteine sulfinate are not affected.
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PMID:Effects of pyridoxal phosphate N-oxide and 2'-hydroxy pyridoxal phosphate on L-aspartate beta-decarboxylase. 116 62

The inhibition by some thiol reagents of partly purified mitochondrial monoamine oxidase (MAO) (EC 1.4.3.4) from rat liver was studied, and the molar content of sulfhydryl groups in the enzyme determined. Sodium nitroprusside and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) inhibited the enzyme, apparently reversibly, while sodium arsenite was not inhibitory. Concentrations of the respective inhibitors causing 50% inhibition after 15 min of preincubation with the enzyme at pH 7.0 and 37 degrees C are 5.80 times 10(-4) M and 4.35 times 10(-5) M. The thiol compounds cysteine, dithiothreitol, and 2-mercaptoethanol did not inhibit MAO. The average number of sulfhydryl groups per mole of enzyme, determined by reaction with DTNB, increased from 3.6 +/- 0.2 freely reacting sulfhydryl groups (n = 4) to 18.4 to total sulfhydryl groups (n = 2) on denaturation with 8 M urea.
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PMID:Essential sulfhydryl groups of rat liver monoamine oxidase. 118 Oct 10

Purified ribulose-bisphosphate carboxylase (EC 4.1.1.39) was strongly and equally inhibited either by ADP or GDP and to a lesser extent by IDP. AMP or ATP exerted little effect on activity. Inhibition by the nucleotide diphosphates was competitive with respect to RuBP and non-competitive with respect to "CO2" and Mg2+, respectively. Treatment of the enzyme with urea or guanidine-HCl resulted in rapid loss of activity that was not restored by dialysis even in the presence of Mg2+ and cysteine. Sodium dodecyl sulfate electrophoresis of 8.0 M urea treated enzyme revealed the presence of a fast-moving (small) sub-unit with molecular weight 14150 and a slower moving (large) sub-unit with molecular weight 68000. Examination of native enzyme by sodium dodecyl sulfate electrophoresis gave sub-units of 13700 and 55500 respectively. The amino acid content standardized to phenylalanine was essentially similar to that from other sources. Arrhenius plots showed a "break" at 29 degrees C with an Ea of 12.34 kcal per mole for the steeper part of the curve and a deltaH of 11.43 kcal per mole while for the less steep region, the Ea was 1.04 kcal per mole and the deltaH 1.92 kcal per mole.
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PMID:Physical properties and metabolite regulation of ribulose bisphosphate carboxylase from Thiobacillus A2. 127 53

The kinetics of the reaction of 3-deoxyhexosulose, DH, with mercaptoethanol, ME, and glutathione, GSH, resemble those of the DH-sulphite reaction, but the stoichiometry of the DH-thiol reaction is 1:2 unlike that of the DH-sulphite reaction which is 1:1. However, the rate determining step in all these reactions is the spontaneous conversion of DH to a reactive intermediate, followed by a rapid reaction of this intermediate with the nucleophile. This is also true of the reaction between DH and N-acetylcysteine, NAC, but this thiol is less reactive than ME or GSH and less than one mole of NAC reacts with each mole of DH. Evidence for instability of NAC at pH 5.5 is presented. Aminothiols (cysteine, homocysteine, cysteamine) undergo a fast reaction with DH followed by a slow release of thiol. The initial reaction is probably formation of a thiazolidine. In the case of cysteine and homocysteine it is suggested that the subsequent slow step is a Strecker degradation reaction. The kinetic behaviour of thiols in cabbage homogenates is reported.
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PMID:Kinetics and mechanism of the reaction between 3-deoxyhexosulose and thiols. 129 50


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