Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Diuron”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62Linked to original sources
PubMed1975

Studies on a phospholipase B from Penicillium notatum. Purification, properties, and mode of action.

1. Phospholipase B which hydrolyzes both the acyl ester bonds of diacylphospholipids (diacyl-hydrolase) and the acyl ester bond of monoacylphospholipids or lysophospholipids, [monoacyl-hydrolase or lysophospholipase, EC 3.1.1.5] was purified from Penicillium notatum about 2000-fold over the crude extract. The final preparation was homogeneous on disc electrophoresis. The apparent molecular weight, determined by gel filtration on Sephadex G-200, was about 116,000. The isoelectric point was pH 4.0. 2. The purified enzyme was a glycoprotein. The carbohydrate content was approximately 30%, consisting of mannose, glucose, and glucosamine. The amino acid composition was also determined. 3. The ratio of monoacyl-hydrolase to diacyl-hydrolase activities was influenced by the physical state of the substrate in the assay system. It was about 1 : 1 or 100 : 1 in the presence of absence of Triton X-100, respectively, and the latter value remained constant throughout the purification procedures. 4. Both enzyme activities had the same pH optimum, 4.0, and were heat-labile. None of the metals tested had any effect on either activity except for Fe2+ and Fe3+. Diisopropyl fluorophosphate at relatively high concentrations completely inhibited both enzyme activities. 5. The Michaelis-Menten constants (Km) of the enzyme for egg lecithin were about 1.5 and 25 mM in the absence and presence of Triton X-100, respectively. The Km value for dicaproyllecithin was 9.8 mM in the absence of Triton X-100. 6. Using a mixture of 1-[14C]stearoyl-lecithin and 2-[14C]oleoyl-lecithin in the presence of Triton X-100 as a substrate, it was found that the P. notatum phospholipase B attacked the acyl ester bonds sequentially, first the 2-acyl and then 1-acyl groups.

Amino Acids↗
PubMed1975

Substrate specificity of carboxypeptidase from Watermelon.

The substrate specificity of carboxypeptidase (F-II) purified from watermelon for various synthetic peptides and esters was examined kinetically. The enzyme showed a broad substrate specificity against various carbobenzoxy- and benzyl-dipeptides. Peptides containing glycine or proline were hydrolyzed slowly by the enzyme. Peptides containing hydrophobic amino acids were hydrolyzed rapidly. The presence of hydrophobic amino acid residues, not only at the C-terminal position but also at the second position and probably the third position from the C-terminal resulted in an increase in the rate of hydrolysis. Inhibition studies with diisopropyl flurophosphate and diastereomers of carbobenzoxy-Phe-Ala demonstrated that the peptidase and esterase activities of the enzyme are both catalyzed by the same site of the enzyme molecule, but the binding sites for peptides and esters seem not to be the same. The enzyme also had amidase activity, which was optimal at pH 7.0.

Amidohydrolases↗
PubMed1975

Further confirmation of carboxypeptidase Y as a metal-free enzyme having a reactive serine residue.

The metal content of carboxypeptidase Y was analyzed by the atomic absorption method. After exhaustive dialysis against an EDTA solution, the enzyme showed no loss of activity nor any significant content of metals (Zh,Mg,Ca,Cu,Mn,Ni,Fe, and Co). The activity was, however, rather sensitive to preincubation with various metals. The reactivity of a serine residue of the enzyme was also reevaluated. Diisopropyl fluorophosphate (DFP) and phenylmethanesulfonyl fluoride (PMSF) stoichiometrically and irreversively inhibited the enzyme. The rate of inactivation with DFP was much faster than that for typsin [EC 3.4.21.4] and chymotrypsin [EC 3.4.21.1.], while the rate with PMSF was one-fifteenth of that for chymotrypsin. The pH-dependence of the inactivation by DFP was similar to that of the enzymatic hydrolysis of acetylphenylalanine ethyl ester. The present results indicate that carboxypeptidase Y is free of metals and has a serine residue with a vital role in the catalytic process, though the functional role of this SH group remains to be clarified.

Apoenzymes↗
PubMed1980

An in vitro protein-synthesizing system with isolated chloroplasts of Sorghum vulgare. An alternate assay system for exogenous template RNA.

A light-dependent in vitro protein-synthesizing system from isolated mesophyll chloroplasts of Sorghum vulgare was characterized. Preincubation of chloroplasts in light at 25 degrees C for 1 h depleted the endogenous templates completely; such preincubated chloroplasts translated exogenously added homologous, heterologous, and synthetic templates efficiently. The fidelity of the system in translating added templates was tested with specific templates. Substantive evidence for the fidelity of the system was obtained by immunological analysis of the specific products, e.g. chloroplast coupling Factor I obtained by the translation of S. vulgare leaf cellular and chloroplast RNAs. The efficiency of the system in translating the exogenous mRNA was also quite high. As the endogenous mRNA was totally depleted during preincubation, and as the system was nonspecific for the source of RNA for translation, these chloroplasts can serve as a simple alternative system for assaying the role of diverse template RNAs.

Amino Acids↗
PubMedDate not supplied

[Microsecond delayed Chlorella fluorescence].

The kinetics of delayed fluorescence between 40 microseconds and 500 microseconds at room temperature, excited by nanosecond light pulses of a nitrogen laser was analysed in terms of exponential components due to the different ways of reduction of the oxidized reaction centre pigment of the second photochemical system of photosynthesis. The details of the laser phosphoroscope of 20 microseconds resolution time are given. The delayed fluorescence of intact samples has 30 microseconds and 150 microseconds components; treatment with DCMU causes quenching, the kinetics remains unchanged; hydroxylamine causes enhancement at lower concentrations and quenching at higher ones, the component of 150 microseconds disappears. These changes corrborate the heterogeneous center model of the microsecond delayed fluorescence.

Chlorella↗
PubMed1994

Function and organization of photosystem I in a cyanobacterial mutant strain that lacks PsaF and PsaJ subunits.

Photosystem I functions as a light-driven plastocyanin-ferredoxin oxidoreductase in the photosynthetic membranes of cyanobacteria and chloroplasts. A mutant strain of the cyanobacterium Synechocystis sp. PCC 6803 that contains a deletion of the psaF gene and a transcriptionally inactive psaJ gene has assembled photosystem I complexes that lack PsaF, a lumenal protein and PsaJ, a 4-kDa hydrophobic protein. The cells of the mutant and wild type strains have similar rates of photosynthetic electron transfer and P700+ rereduction under linear and cyclic electron transfer conditions. Analysis of flash-induced absorption transients at 700 nm demonstrate that the absence of PsaF in purified mutant photosystem I did not affect the rate of P700 rereduction by cytochrome c553. Therefore, PsaF is not essential for docking of cytochrome c553. We also studied the organization of the proteins of mutant and wild type photosystem I by comparing their accessibility to digestion by thermolysin or to removal by 1 M NaI. The PsaA-PsaB subunits were more easily degraded by thermolysin in the mutant photosystem I. Thermolysin cleavage of PsaB yielded two major fragments that were immunoreactive with an antibody raised against the C terminus of PsaB. The N termini of these PsaB peptides mapped at Ile482 and Ile498 residues, thus identifying a surface-exposed domain of the core of photosystem I. The PsaE subunit could be removed by 1 M NaI and was rapidly digested by thermolysin in the mutant but not in the wild type photosystem I. Therefore, PsaF and PsaJ subunits of photosystem I have dispensable accessory roles in the function and organization of the complex.

Amino Acid Sequence↗
PubMedDate not supplied

[Characteristics of different growth stages of the blue-green alga Anacystis nidulans (Synechococcus)].

The rate of growth of the blue-green alga Anacystis nidulans is highest during the first 5--8 days but the number of the cells increases up to 30 days when the stationary phase takes place (30--60 days). The content of chlorophyll is almost constant during the first 20 days of growth while the content of phycocyanin increases; then the content of the both pigments decreases. The rate of O2 evolution and the rate of electron transport to ferricyanide decrease exponentionally during the first 10 days of growth. The rate of endogenous respiration and the rate of O2 absorption, induced by methylviologen in the light in the presence of DCMU decrease more slowly. At the same time, the rate of O2 absorption in the presence of methylviologen without DCMU and the rate of TTC reduction in the darkness increase and later decrease. The rate of TTC reduction in the light increases up to 30--40 days and then decreases. The rate of the cell death in the darkness decreases when the age of the "light" culture is 50 days. Addition to the medium of its main components does not increase the rate of growth of the culture after 10 days of its growth. Addition of CaCl2, glucose, and asparagic acid increases the rate of growth of the 3-day-old culture. Addition of phosphorus inhibits growth. Argon favours growth of the culture. The cells are rapidly discoloured in conditions of hampered gas exchange; they die rapidly also in the presence of DCMU, methylviologen, and KCN.

Chlorophyll↗