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PubMed1975

Effect of protein concentration on the molecular weight of delta5-3-ketosteroid isomerase.

The molecular weight of delta-5-3-ketosteroid isomerase from Pseudomonas testosteroni was determined by means of sedimentation equilibrium and exclusion chromatography over a wide range of enzyme concentrations in 0.2 M potassium phosphate buffer, pH 7.0. In addition, the sedimentation constant of the enzyme was determinded over an extended range of concentrations. The enzyme was found to have a molecular weight of 26,000 plus or equal to 1,000, suggesting that it is a dimer of identical or similar 13,400 molecular weight polypeptide chains. In the ultracentrifuge this dimeric species was found to undergo aggregation at enzyme concentrations above 2 mg per ml and dissociation at enzyme concentrations below 0.05 mg per ml. Exclusion chromatography studies indicate that under the conditions of chromatography the oligomeric enzyme is partially dissociated at enzyme concentrations in the range 0.2 to 0.002 mug per ml. These results suggest that under conditions of enzyme assay in 0.2 M potassium phosphate buffer, pH 7.0, isomerase is in a monomeric state of aggregation.

Binding Sites↗

PubMed1975

Mechanistic implications of the pH independence of inhibition of phosphoglucose isomerase by neutral sugar phosphates.

In contrast to the strongly pH-dependent inhibition of phosphoglucose isomerase by substrate analogues with a free carboxyl group, inhibition of this enzyme by neutral sugar phosphates is essentially invariant between pH 7 and 9. Competitive inhibition constants for glucitol 6-phosphate (40 muM), arabinose 5-phosphate (50 muM), and erythritol 4-phosphate (100 muM) were found to be of the same order of magnitude as that reported previously for substrate binding constants (50 to 240 muM). The unique exception is erythrose 4-phosphate whose Ki (0.7 muM, independent of pH) reflects a tightness of binding similar to that found at pH values near or below neutrality for the transition state analogue 5-phosphorarabinonate. The pH independence of inhibition by erythrose 4-phosphate and other neutral sugar phosphates may reflect a mode and locus of binding to phosphoglucose isomerase different from that of the aldonate inhibitors.

Animals↗

PubMedDate not supplied

[Effect of vitamins and various amino acids on glucose isomerase biosynthesis by Streptomyces albogriseolus culture].

The effect of vitamins (B1, B2, B3, B6, B12, H, PP and folic acid) and amino acids (glutamic and aspartic acids) on glucose isomerase biosynthesis was studied in Streptomyces albogriseolus. These compounds were added either alone or in combinations to different growth media (synthetic and complex). The results were processed using mathematical methods, and the following mixture of vitamins and amino acids was proposed to be added to the complex fermentation medium: B2, 10 micrograms/L; B6, 10 micrograms/L; H, 1 microgram/L; aspartic acid, 0.01 microM. The production of glucose isomerase rose more than 1.5 times after such additions.

Aldose-Ketose Isomerases↗

PubMed1988

Variants of phosphohexose isomerase in gastrointestinal and mammary carcinoma: isoelectric focusing patterns of normal and tumor tissues derived from surgical specimens of the same patient.

The occurrence of charge variants of phosphohexose isomerase was elucidated in cancerous and, for comparison, in noncancerous tissues obtained from the same organ. Surgical specimens from 35 patients with gastrointestinal and mammary carcinoma were studied by means of the isoelectric focusing (IEF) technique. Differences in the IEF pattern could be demonstrated in 90% of the patients with gastric cancer. Corresponding values for the patients with colorectal and mammary carcinoma were 50 and 73%, respectively. Almost all normal specimens proved to be monomorphic, revealing only the major basic band with a pI of 9.1. In most of the tumors, additional bands of pI 8.9 and 8.6 were found. This "typical" IEF pattern in tumor tissues was observed in 60% of gastric and 73% of mammary tumors, but in only 36% of colorectal tumors. The results obtained suggest that the IEF pattern of phosphohexose isomerase in tumor tissue might be a useful tool for tumor diagnosis.

Breast↗

PubMed1979

Purification of hog liver isomerase. Mechanism of isomerization of 3-alkenyl and 3-alkynyl thioesters.

A hog liver enzyme that catalyzes the reversible conversion of 3-acetylenic fatty acyl thioester to (+)-2,3-dienoyl fatty acyl thioester has been purified to homogeneity. The enzyme is not inhibited by the allenic product that it generates. The same homogenous enzyme catalyzes the conversions of 3-cis- or 3-trans-acyl Coenzyme A derivatives to 2-trans-acyl-CoA derivatives. Four forms of the isomerase differing in charge (pI = 6.57, 6.83, 7.01, and 7.27) have been separated by isoelectric focusing. Ultracentrifugation and sodium dodecyl sulfate-gel electrophoresis indicate that each of these enzyme forms is dimeric and composed of two 45,000-dalton subunits. With 3-acetylenic substrates, all enzyme forms exhibit broad specificity for chain length (C6 to C12) and for the thioester moiety (N-acetylcysteamine (NAC), pantetheine, or CoA). The 3-cis and 3-trans olefinic substrates are active only in the form of their coenzyme A derivatives; their NAC thioesters inhibit competitively. Mechanistic studies favor an isomerization pathway by way of carbanion intermediates. The acetylene-allene isomerase described here and the reported crotonase-catalyzed hydration of allenic thioesters (Branchini, B.R., Miesowicz, F.M., and Bloch, K. (1977) Bioorg. Chem. 6, 49-52) may be responsible for the degradation of naturally occurring acetylenic and allenic acids.

Acyl Coenzyme A↗

PubMed1977

[A comparison of serum phosphohexose isomerase and sialyl transferase activities in patients with malignant disease].

The diagnostic value of serum sialyl transferase, phosphohexose isomerase and lactate dehydrogenase determinations is discussed in respect to patients with malignant diseases. It was found that 80 % of the investigated cases showed an increase in serum sialyl transferase activity. Phosphohexose isomerase was elevated in 46.6 % and lactate dehydrogenase in 23.3% of the cases. The serum sialyl transferase activity was within the normal range in 13.3% of the patients. It is concluded that although the serum sialyl transferase activity is of great diagnostic significance in cases of suspected malignancy, total reliance cannot be placed on the determination of this sole parameter, but only in conjunction with others.

Breast Neoplasms↗

PubMed1980

Concurrent measurements of carcinoembryonic antigen, glucosephosphate isomerase, gamma-glutamyltransferase, and lactate dehydrogenase in malignant, normal adult, and fetal colon tissues.

Carcinoembryonic antigen and activities of glucosephosphate isomerase (EC 5.3.1.9), gamma-glutamyltransferase (EC 2.3.2.2), and lactate dehydrogenase (EC 1.1.1.27) were measured in aqueous extracts of fetal, normal adult, and malignant human colon tissues. Fetal colon, as well as primary and metastatic colon tumor tissue, showed higher activities of these analytes than did normal adult human colon. Liver metastases of colon cancer gave the highest values, normal adult human colon the lowest. Statistically, these differences were more striking in the case of carcinoembryonic antigen and glucosephosphate isomerase than for gamma-glutamyltransferase or lactate dehydrogenase. In contrast to the other markers, gamma-glutamyltransferase activity was lower in fetal organs than in normal adult colon and colon tumors. These results are consistent with earlier observations that activities of these markers are significantly increased in the blood of patients with metastatic colon cancer.

Adult↗

PubMed1984

Primary structure of human triosephosphate isomerase.

Human placental triosephosphate isomerase was isolated by an improved procedure and recovered with the highest specific activity ever reported. Employing this purification procedure, sufficient amounts of the enzyme were obtained for detailed primary structural studies. For sequences analysis, the enzyme was reduced and carboxymethylated and subjected to tryptic and chymotryptic digestions. The peptide mixtures were separated by high-performance liquid chromatography using octyl or alkylphenyl reverse-phase columns and trifluoroacetic acid/acetonitrile gradient elution systems. Sequence analyses of the intact enzyme, tryptic, chymotryptic, and cyanogen bromide peptides were accomplished using high-sensitivity solid-phase sequencing procedures with either 4-N,N-dimethylaminoazobenzene-4'-isothiocyanate or phenylisothiocyanate. The primary structure of human triosephosphate isomerase is constructed from the alignment of the tryptic peptides with the analysis of the overlapping chymotryptic peptides. The enzyme is a dimeric molecule consisting of two identical polypeptide chains with 248 amino acid residues and a calculated subunit molecular mass of 26,750 daltons. A comparison of the amino acid sequences from the human placental enzyme and from other species such as rabbit, chicken, and coelacanth muscles showed relatively high sequence homology, indicating that the evolution of the enzyme is very conservative. The amino acids of the active-site pocket and the subunit-subunit contact sites exhibit few changes.

Amino Acid Sequence↗

PubMed1983

Identification of the target amino acids in the site-specific inactivation of triose phosphate isomerase by ferrate anion.

Ferrate anion, an analog of orthophosphate anion, very rapidly inactivates triose phosphate isomerase from chicken muscle. The inactivation can be prevented by the presence of competitive inhibitors. Of the 247 amino acids known to be present in each of the identical monomers of this dimeric enzyme, Trp-168, located in the active site pocket, as well as Trp-191 and His-248 are destroyed. The partial loss of Tyr-164 also occurs. Trp-168 is known from published crystallographic studies to be located in the active site cavity harboring Glu-165. The gamma-carboxylate group of Glu-165 is believed to serve as the nucleophile which catalyzes the isomerization. Tyr-164, Glu-165, and Trp-168 are known to be conserved in all of the triose phosphate isomerases which have been sequenced, including those obtained from mammals, chicken, fish, yeast, and bacteria. It is suggested that the chemical modification of Trp-168 alters its shape and hydrophobic character in a manner that adversely affects the conformation of the active site cavity. When the chicken enzyme is treated with ferrate in the presence of the competitive inhibitor phosphoglycolate, only His-248 is destroyed. Thus, His-248, which is the COOH-terminal amino acid, cannot be essential for activity. This observation is consistent with the knowledge that it is not invariant in the enzyme from various species.

Amino Acids↗

PubMed1984

X-ray crystal structure of D-xylose isomerase at 4-A resolution.

The structure of D-xylose isomerase from Streptomyces rubiginosus has been determined at 4-A resolution using multiple isomorphous phasing techniques. The folding of the polypeptide chain has been established and consists of two structural domains. The larger domain consists of eight beta-strand alpha-helix (beta alpha) units arranged in a configuration similar to that found for triose phosphate isomerase, 2-keto-3-deoxy-6-phosphogluconate aldolase, and pyruvate kinase. The smaller domain forms a loop away from the larger domain but overlapping the larger domain of another subunit so that a tightly bound dimer is formed. The tetramer then consists of two such dimers. The location of the active site in the enzyme has been tentatively identified from studies using a crystal grown from a solution containing the inhibitor xylitol.

Aldose-Ketose Isomerases↗

PubMed1982

Nucleotide sequence of the triose phosphate isomerase gene of Saccharomyces cerevisiae.

The gene coding for the glycolytic enzyme triose phosphate isomerase (TPI1) was isolated from a yeast library in the shuttle vector pYE13. Selecting for a deletion mutant of the plasmid which enhances expression of the otherwise dormant yeast gene in E. coli facilitated the identification of the coding region. The DNA sequences of the wild type and mutant genes were determined by chemical methods. The 5' flanking region of the wild-type TPI1 resembles the analogous regions of the yeast genes coding for two other glycolytic enzymes. The sequence of the deletion mutant indicates that, upstream from -65 in the 5' flanking region, 3.3 kilobases have been lost from entirely within the yeast insert. The mutation reduces enzyme activity by tenfold in yeast, and its implications for the expression of the gene in yeast and E. coli are discussed. The amino acid sequence deduced from the nucleotide order is consistent with the electron density map of the protein as well as the sequence of its N-terminal 16 amino acids and amino acid composition. The amino acid sequence is approximately 50% homologous with the triose phosphate isomerases from rabbit, chicken, and coelacanth and 37% homologous with the Bacillus stearothermophilus enzyme. Residues which are thought to be catalytically important are conserved.

Amino Acid Sequence↗

PubMed1980

Glucose phosphate isomerase isoenzyme patterns in bovine lymphoblastoid cell lines infected with Theileria annulata and T parva, with an improved enzyme visualisation method using meldola blue.

Five strains of Theileria annulata from three geographically different areas and one strain of T parva were grown in bovine lymphoblastoid cell lines. Lysates of the parasitised cells were examined by thin layer starch gel electrophoresis for multiple forms of the enzyme glucose phosphate isomerase. A reported difference between the glucose phosphate isomerase isoenzyme patterns of T annulata and T parva was confirmed. Cultures of one strain of T annulata grown in cells derived from four different cattle showed similar host and parasite isoenzyme patterns. Two strains of T annulata and one strain of T parva grown in lymphoid cells derived from the same animal showed identical host cell isoenzyme patterns whereas the isoenzyme pattern associated with each parasite was different. Strains of T annulata from different geographical areas showed major differences in their isoenzyme patterns, but no differences were detected between strains from the same geographical area. Meldola blue was found to be superior to phenazine methosulphate as an intermediate electron acceptor in the visualisation of enzyme activity.

Animals↗

PubMed1978

Prostaglandin biosynthesis in platelets: demonstration and role of prostaglandin H2 leads to E2 isomerase.

Double-labeled [3H/14C]-prostaglandin endoperoxide H2 was used to assess the presence in platelets of enzymatic activity for conversion of the endoperoxides to prostaglandin E2. This enzymatic activity (prostaglandin H2 leads to E2 isomerase) involves the selective removal of a hydrogen from the C-9 carbon atom of the endoperoxide molecule and is subject to an isotope discriminatory effect against tritium-labeled molecules. Rabbit washed platelet suspension was pre-incubated for 1 min, with imidazole (1 mM) to inhibit thromboxane A2 generation and [3H/14C]--prostaglandin H2 was added. Analysis of the [3H] and [14C] radioactive products in incubations with native vs. heat denatured platelets indicated that native platelets convert the endoperoxide enzymatically to mainly prostaglandin E2. Thus, although arachidonic acid released endogenously or added exogenously to platelets is converted mainly to thromboxane B2 and 120H-17:3 acid, platelets appear to possess prostaglandin H2 leads to E2 isomerase activity which becomes manifested when thromboxane synthetase activity is inhibited.

Animals↗

PubMedDate not supplied

Phosphohexose isomerase activity as a tumor marker in hepatoma bearing rats (Yoshida A.H. 130).

The object of this study was to examine if there exists, analogously to what happens in human cancer patients, elevation of phosphohexose isomerase activity (PHI, EC 5.3.1.9) in the serum of animals bearing an experimental tumor and, if so, whether such increases were related to the progress of the tumor, as in humans. The behavior of the same enzyme activity within the tumor itself was also studied. Significant correlations were found between serum elevations of PHI and hepatoma growth. These correlations, moreover, emerge at a very early stage. On the other hand, no relation appears to exist between phosphohexose isomerase activity in the tumor and that in the blood. The two divisions, furthermore, do not seem to interact. These results may prove interesting prospectives for the monitoring of human cancer.

Animals↗

PubMed1981

[Glucosephosphate isomerase polymorphism in the teleost fish loach Misgurnus fossilis].

Using polyacrylamide gel disc-electrophoresis, the isoenzymic patterns of glucosephosphate isomerase (EC 5.3.1.9) in some tissues of adult loaches Misgurnus fossilis and in the unfertilized eggs, embryos and developing larvae of this species were determined. The sensitivity of the enzyme in the eggs and some tissues to inactivation at 45 degrees and to inhibition by high concentrations of fructose-6-phosphate was investigated. A comparison of the experimental data on the subunit composition of the bulk of the detected isoenzymes with literary data was carried out. A conclusion on the expression of four non-allelic glucose phosphate isomerase genes in the loach, i. e. two genes determining the structure of B-subunits and two genes determining the structure of B-subunits, was made. Besides, there were detected the alleles of both types of genes.

Animals↗

PubMedDate not supplied

[Conversion of D-glucose into D-fructose in a column reactor with immobilized glucose isomerase].

Conversion of D-glucose into D-fructose in a column reactor of a continuous type was studied using an immobilized enzyme, glucose isomerase from Actinomyces olivocinereus. The effective parameters of Km, Vmax, energy activation at various flow rates were calculated. During 32 days of continuous operation the enzyme activity fell down to 84% of the initial level. A system of recirculation was employed to use immobilized glucose isomerase with a low activity.

Actinomyces↗

PubMed1978

Purification, crystallization and properties of triosephosphate isomerase from human skeletal muscle.

1. Triosephosphate isomerase (D-glyceraldehyde-3-phosphate ketoisomerase, EC 5.3.1.1) from human skeletal muscle was purified to homogeneity and crystallized. The crystalline enzyme preparation was resolved on polyacrylamide-gel electrophoresis into three isoenzymes. 2. The molecular weight of the enzyme estimated by gel filtration method was found to be 57,400 +/- 3000. Molecular weight determination under dissociation conditions indicated a dimeric subunit structure of the enzyme. 3. The apparent Km for D-glyceraldehyde-3-phosphate as substrate is 0.34 mM, and for dihydroxyacetone phosphate, 0.61 mM. Vmax of the reaction is, respectively, 7200 and 660 units/mg protein at 25 degrees C and pH 7.5. 4. Molecular and kinetic properties of triosephosphate isomerase from human skeletal muscle are very similar to those of rabbit muscle enzyme.

Carbohydrate Epimerases↗

PubMed1994

The sequence of xylose isomerase gene from Streptomyces diastaticus No. 7 M1033.

The DNA sequence of the xylose isomerase gene from Streptomyces diastaticus No. 7 M1033 from Hainan Province has been determined. The structure gene of the enzyme is composed of 1161bp, corresponding to 387 amino acid residues. The G+C content of the gene is 72.1%. The probability of G or C on the third position of the codon is 98%. At the level of amino acids, this xylose isomerase displays high homology with those from other Actinomycete strains, particularly those from Streptomyces strains.

Aldose-Ketose Isomerases↗