scholarly journals The Arabidopsis TCH4 Xyloglucan Endotransglycosylase (Substrate Specificity, pH Optimum, and Cold Tolerance)

1997 ◽  
Vol 115 (1) ◽  
pp. 181-190 ◽  
Author(s):  
M. M. Purugganan ◽  
J. Braam ◽  
S. C. Fry
Keyword(s):  
Substrate Specificity ◽  
Cold Tolerance ◽  
Xyloglucan Endotransglycosylase ◽  
Ph Optimum

scholarly journals Characterization of phospholipase A2 in monocytic cell lines. Functional and biochemical aspects of membrane association

1991 ◽  
Vol 276 (3) ◽  
pp. 631-636 ◽  
Author(s):  
W Rehfeldt ◽  
R Hass ◽  
M Goppelt-Struebe
Keyword(s):  
Substrate Specificity ◽  
Phospholipase A2 ◽  
Cell Lines ◽  
Cytosolic Phospholipase A2 ◽  
Biologically Active ◽  
Ph Optimum ◽  
Monocytic Cell ◽  
Cytosolic Phospholipase ◽  
Membrane Bound ◽  
Phospholipase A2 Activity

Phospholipase A2 activity was characterized in the human monocytic tumour-cell lines U937 and THP1. The enzyme showed an alkaline pH optimum and substrate specificity for arachidonoyl-phosphatidylcholine. The activation of phospholipase A2 required bivalent cations (Ca2+ greater than Mg2+ = Sr2+ greater than Ba2+). Investigation of the subcellular distribution of the enzyme revealed that the phospholipase A2 activity was shifted to the cytosol in the presence of EDTA, indicating that the association of the enzyme with the cellular membranes is Ca2+ (bivalent-cation)-dependent. Stimulation of THP1 cells for 2-4 h with the phorbol ester phorbol 12-myristate 13-acetate (PMA) activated cytosolic and membrane-bound phospholipase A2. At this time, no effect of PMA on phospholipase A2 activity was observed in the less mature U937 cells. However, when both cell lines were induced to differentiate along the monocytic pathway by a 2-3-day treatment with PMA, the cells released significant amounts of arachidonic acid and prostanoids. Compared with undifferentiated control cells, these PMA-differentiated cells showed a decrease in cytosolic phospholipase A2 activity and an increase in membrane-bound activity. Membrane-bound and cytosolic enzyme showed the same pH optimum, Ca(2+)-dependency and substrate specificity. These data indicate that membrane-bound and cytosolic phospholipase A2 activities represent one enzyme and that the membrane-bound form is the biologically active phospholipase A2.

scholarly journals Enzymic synthesis of N-acetyl-l-phenylalanine in Escherichia coli K12

1971 ◽  
Vol 124 (5) ◽  
pp. 905-913 ◽  
Author(s):  
R. V. Krishna ◽  
P. R. Krishnaswamy ◽  
D. Rajagopal Rao
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Amino Acid ◽  
Substrate Specificity ◽  
Acetyl Coa ◽  
Ph Optimum ◽  
E Coli ◽  
Enzymic Synthesis ◽  
Escherichia Coli K12

1. Cell-free extracts of Escherichia coli K12 catalyse the synthesis of N-acetyl-l-phenylalanine from acetyl-CoA and l-phenylalanine. 2. The acetyl-CoA–l-phenylalanine α-N-acetyltransferase was purified 160-fold from cell-free extracts. 3. The enzyme has a pH optimum of 8 and catalyses the acetylation of l-phenylalanine. Other l-amino acids such as histidine and alanine are acetylated at slower rates. 4. A transacylase was also purified from E. coli extracts and its substrate specificity studied. 5. The properties of both these enzymes were compared with those of other known amino acid acetyltransferases and transacylases.

scholarly journals The metabolism of succinic semialdehyde by a psychrophilic basidiomycete

1969 ◽  
Vol 47 (5) ◽  
pp. 809-813 ◽  
Author(s):  
Parker N. Davies ◽  
Gary A. Strobel
Keyword(s):  
Substrate Specificity ◽  
Succinic Acid ◽  
Crude Extract ◽  
Major Portion ◽  
Succinic Semialdehyde ◽  
Ph Optimum ◽  
Succinic Semialdehyde Dehydrogenase ◽  
Coenzyme Specificity ◽  
Semialdehyde Dehydrogenase

A plant-pathogenic psychrophilic basidiomycete metabolized succinic semialdehyde-14C to 14CO2 and various compounds labelled with 14C that appeared in the cation, anion, and neutral fractions of the fungus. The major portion of succinic semialdehyde taken into the cell was oxidized to succinic acid. A crude extract of the fungus possessed a soluble succinic semialdehyde dehydrogenase that was characterized as to stability, pH optimum, Km, substrate specificity, and coenzyme specificity. Electrophoresis of the crude extract on acrylamide gels showed that there were either several enzymes able to oxidize succinic semialdehyde or that several forms of the same enzyme exist in the fungus.

Purification and characterization of a post-proline dipeptidyl aminopeptidase fromStreptococcus cremorisAM2

1990 ◽  
Vol 57 (1) ◽  
pp. 89-99 ◽  
Author(s):  
Mary Booth ◽  
Ide Ni Fhaoláin ◽  
P. Vincent Jennings ◽  
Gerard O'Cuinn
Keyword(s):  
Molecular Weight ◽  
Amino Acid ◽  
Substrate Specificity ◽  
Purification And Characterization ◽  
Ph Optimum ◽  
Cheese Ripening ◽  
Streptococcus Cremoris ◽  
Scissile Bond ◽  
Dipeptidyl Aminopeptidase

SummaryThe present study describes the purification of a post-proline dipeptidyl aminopeptidase from the cytoplasm ofStreptococcus cremorisAM2. On the basis of its elution from a calibrated Sephadex G200 column, the enzyme had a molecular weight of 117000 and exhibited a broad pH optimum activity between 6·0 and 9·0. The activity was most comprehensively inhibited by phenylmethylsulphonylfluoride and more modestly inhibited by 1,10-phenanthroline and 8-hydroxyquinoline but not by EDTA. A range of peptides containing either proline or alanine as the penultimate amino acid residue could act as substrates. The presence of proline on the carboxy side of the scissile bond prevented hydrolysis. However the enzyme could release Pro-Pro from Pro-Pro-Gly-Phe-Ser-Pro. The significance of this substrate specificity is considered in the context of removal of either single proline residues or prolylproline sequences from oligopeptides during cheese ripening.

scholarly journals Purification, Properties, and Characterization of Recombinant Streptomyces sp. Strain C5 DoxA, a Cytochrome P-450 Catalyzing Multiple Steps in Doxorubicin Biosynthesis

1999 ◽  
Vol 181 (1) ◽  
pp. 298-304 ◽  
Author(s):  
Robbie J. Walczak ◽  
Michael L. Dickens ◽  
Nigel D. Priestley ◽  
William R. Strohl
Keyword(s):  
Substrate Specificity ◽  
Soluble Protein ◽  
Biosynthetic Pathway ◽  
Temperature Optimum ◽  
Ph Optimum ◽  
Streptomyces Sp ◽  
Properties And Characterization ◽  
Cytochrome P 450 ◽  
Late Stages

ABSTRACT DoxA is a cytochrome P-450 monooxygenase involved in the late stages of daunorubicin and doxorubicin biosynthesis that has a broad substrate specificity for anthracycline glycone substrates. Recombinant DoxA was purified to homogeneity from Streptomyces lividanstransformed with a plasmid containing the Streptomyces sp. strain C5 doxA gene under the control of the strong SnpR-activated snpA promoter. The purified enzyme was a monomeric, soluble protein with an apparent M rof 47,000. Purified DoxA catalyzed the 13-hydroxylation of 13-deoxydaunorubicin, the 13-oxidation of 13-dihydrocarminomycin and 13-dihydrodaunorubicin, and the 14-hydroxylation of daunorubicin. The pH optimum for heme activation was pH 7.5, and the temperature optimum was 30°C. The k cat/Km values for the oxidation of anthracycline substrates by purified DoxA, incubated with appropriate electron-donating components, were as follows: for 13-deoxydaunorubicin, 22,000 M−1 · s−1; for 13-dihydrodaunorubicin, 14,000 M−1 · s−1; for 13-dihydrocarminomycin, 280 M−1 · s−1; and for daunorubicin, 130 M−1 · s−1. Our results indicate that the conversion of daunorubicin to doxorubicin by this enzyme is not a favored reaction and that the main anthracycline flux through the late steps of the daunorubicin biosynthetic pathway catalyzed by DoxA is likely directed through the 4-O-methyl series of anthracyclines.

Immunological and biochemical evidence for identity of tartrate-resistant isoenzymes of acid phosphatases from human serum and tissues.

1980 ◽  
Vol 26 (3) ◽  
pp. 420-422 ◽  
Author(s):  
K W Lam ◽  
P Lee ◽  
C Y Li ◽  
L T Yam
Keyword(s):  
Acid Phosphatase ◽  
Substrate Specificity ◽  
Human Serum ◽  
Giant Cell ◽  
Bone Tumor ◽  
Biochemical Characterization ◽  
Acid Phosphatases ◽  
Ph Optimum ◽  
Human Spleen ◽  
Biochemical Evidence

Abstract We purified acid phosphatase isoenzyme 5b from a human spleen affected by leukemic reticuloendotheliosis and used it to produce a specific antiserum. The antiserum was used to show complete immunological identity among isoenzymes 5a and 5b in human serum, and 5b isolated from a giant-cell bone tumor and from the spleen of a case of Hodgkin's disease. Acid phosphatase 5b in a giant-cell bone tumor was isolated for biochemical characterization. Its pH optimum and substrate specificity were very similar to those of isoenzyme 5b from human spleen.

Pea alcohol dehydrogenase: Substrate specificity and binding of coenzyme to enzyme

1979 ◽  
Vol 44 (2) ◽  
pp. 631-636 ◽  
Author(s):  
Marie Stiborová ◽  
Roman Lapka ◽  
Noemi Nováková ◽  
Sylva Leblová
Keyword(s):  
Alcohol Dehydrogenase ◽  
Substrate Specificity ◽  
Competitive Inhibitor ◽  
Substrate Oxidation ◽  
Enzyme Protein ◽  
Ph Optimum ◽  
Substrate Reduction ◽  
Noncompetitive Inhibitor ◽  
Ph Dependent ◽  
Broad Specificity

Pea alcohol dehydrogenase (EC 1.1.1.1) shows a broad specificity with respect to aldehydes and alcohols. The pH-optimum of substrate oxidation is 8.7 and of substrate reduction 7.0. The enzyme is inhibited by ATP, adenosine, and adenine. The inhibition is competitive with respect to NAD. The inhibition by ATP is pH-dependent. The competitive character of the inhibition by adenine and its derivatives with respect to NAD indicates the importance of the adenine moiety of the coenzyme for its binding to the enzyme. Phenanthroline is a competitive inhibitor with respect to NAD, a mixed inhibitor with respect to ethanol and a noncompetitive inhibitor with respect to acetaldehyde. Experiments carried out simultaneously with ATP and phenanthroline show that the adenine moiety of NAD does not bind via the zinc atom to the enzyme protein.

Phenol oxidase activity of a monogenean, Paramazocraes thrissocles

1986 ◽  
Vol 60 (3) ◽  
pp. 234-238
Author(s):  
T. Thangaraj ◽  
A. Vinayakam ◽  
K. Nellaiappan
Keyword(s):  
Substrate Specificity ◽  
Metal Ions ◽  
Oxidase Activity ◽  
Phenol Oxidase ◽  
Maximum Activity ◽  
Ph Optimum ◽  
Phenol Oxidase Activity ◽  
Eggshell Formation ◽  
Chelating Compounds

AbstractThe phenol oxidase of a monogenean, Paramazocraes thrissocles, oxidizes phenolic amines more effectively than other phenols studied. Based on the substrate specificity, the probable substrate for eggshell formation has been suggested. The enzyme shows the pH optimum of 7–2. At 40°C it shows maximum activity. Proenzyme is activated by metal ions and detergents. Copper chelating compounds strongly inhibit the enzyme.

scholarly journals A study of the metabolism of l-αγ-diaminobutyric acid in a Xanthomonas species

1969 ◽  
Vol 114 (1) ◽  
pp. 107-115 ◽  
Author(s):  
D. Rajagopal Rao ◽  
K. Hariharan ◽  
K. R. Vijayalakshmi
Keyword(s):  
Substrate Specificity ◽  
Aspartic Acid ◽  
Acid Metabolism ◽  
Ph Optimum ◽  
Diaminobutyric Acid ◽  
Oxaloacetic Acid ◽  
Binding Agents ◽  
Xanthomonas Species ◽  
High Degree

1. l-αγ-Diaminobutyric acid is metabolized in Xanthomonas sp. to aspartic β-semialdehyde, aspartic acid and oxaloacetic acid. 2. Aspartic β-semialdehyde is formed from diaminobutyric acid by a pyruvate-dependent γ-transamination. 3. The transaminase has a pH optimum of 9 and exhibits a high degree of substrate specificity, as analogues of diaminobutyric acid and pyruvate are inert in the system. The transaminase is inhibited by carbonyl-binding agents such as hydroxylamine. 4. Aspartic acid is formed from aspartic β-semialdehyde by an NAD+-dependent dehydrogenation. 5. The dehydrogenase has a pH optimum of 8·5 and is a thiol enzyme. It is specific for aspartic β-semialdehyde but analogues of NAD+ such as 3-acetylpyridine–adenine dinucleotide and deamino-NAD are partly active in the system. 6. The significance of these reactions is discussed in relation to diaminobutyric acid metabolism in plants and mammalian systems.

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