Search results for "Isozyme"
showing 10 items of 102 documents
Acid Carboxypeptidases in Grains and Leaves of Wheat, Triticum aestivum L
1986
Extracts of resting and germinating (3 days at 20 degrees C) wheat (Triticum aestivum L. cv Ruso) grains rapidly hydrolyzed various benzyloxycarbonyldipeptides (Z-dipeptides) at pH 4 to 6. Similar activities were present in extracts of mature flag leaves. Fractionation by chromatography on CM-cellulose and on Sephadex G-200 showed that the activities in germinating grains were due to five acid carboxypeptidases with different and complementary substrate specificities. The wheat enzymes appeared to correspond to the five acid carboxypeptidases present in germinating barley (L Mikola 1983 Biochim Biophys Acta 747: 241-252). The enzymes were designated wheat carboxypeptidases I to V and their …
Studies on the Mechanism of Inhibition by Phosphinothricin of Glutamine Synthetase Isolated from Triticum aestivum L.
1986
Summary The activity of glutamine synthetase (EC 6.3.1.2) isolated from roots and leaves of wheat is strongly inhibited by phosphinothricin. As revealed by gel filtration and kinetic studies the mechanism of inhibition appears to be irreversible. The results indicate that the rate limiting step of the reaction of the inhibitor with the chloroplast glutamine synthetase is not the initial, but the following reaction. However, of root glutamine synthetase the irreversible inhibition follows a second order reaction depending on the concentration of the enzyme and of phosphinothricin and the rate limiting step is the formation of the initial enzyme-inhibitor complex. According to the kinetic dat…
The Aerobic and Anaerobic Respiratory Chain of Escherichia coli and Salmonella enterica: Enzymes and Energetics.
2014
Escherichia coli contains a versatile respiratory chain that oxidizes 10 different electron donor substrates and transfers the electrons to terminal reductases or oxidases for the reduction of six different electron acceptors. Salmonella is able to use two more electron acceptors. The variation is further increased by the presence of isoenzymes for some substrates. A large number of respiratory pathways can be established by combining different electron donors and acceptors. The respiratory dehydrogenases use quinones as the electron acceptors that are oxidized by the terminal reductase and oxidases. The enzymes vary largely with respect to their composition, architecture, membrane topolog…
Differential function of the phosphoglucomutase isozymes PGM1 and PGM2
1979
A total of 13 metabolites thought to be possibly inhibitory were tested for their influence on PGM isozyme activities, each at several different concentrations. The analysis of statistical significance was based on enzyme activities obtained by densitometric measurements of starch gels. Five of the substances were found to inhibit PGM activity, three of which definitely and a further one probably led to a significantly stronger inhibition of the isozymes of the PGM2 locus than of PGM1 isozymes. They are (1) fructose-1,6-diphosphate, (2) adenosine triphosphate, (3) citrate, and (4) possibly 2,3-diphosphoglycerate. Thus, PGM1 isozymes proved to function better in hard or perhaps marginal meta…
SULFUR ANALOGUES OF POLYCHLORINATED DIBENZO-p-DIOXINS, DIBENZOFURANS AND DIPHENYL ETHERS AS INDUCERS OF CYP1A1 IN MOUSE HEPATOMA CELL CULTURE AND STR…
1994
Three sulfur-containing compounds, 2,3,7,8-tetrachlorothianthrene (TCTA), 2,3,7,8-tetrachlorodibenzothiophene (TCDT), and 3,3[prime],4,4[prime]-tetrachlorodiphenyl sulfide (TCDPS), were analyzed for their CYP1A1-inducing potencies--measured as aryl hydrocarbon hydroxylase (AHH) and 7-ethoxyresorufin O-deethylase (EROD) activities--in mouse hepatoma cell culture Hepa-1. Marked differences in the induction potencies were observed among the three compounds studied and between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and its sulfur analogue. The estimated EC50 values for TCDD, TCTA, and TCDT were about 8 pM, 700 pM, and 7.5 nM, respectively. TCDPS did not elicit any AHH/EROD induction. Compar…
Chapter 17: The cholinesterases: a discussion of some unanswered questions
1993
Publisher Summary During the past three decades, a vast body of specificity and kinetic data relating to the cholinesterases has accumulated, which must now be explained by the extremely interesting new sequence and X-ray crystallographic results presented by MassouliC et al. As this chapter shows, the cholinesterases are remarkable among enzymes in having a broad specificity embracing both charged and uncharged substrates but with a clearly expressed preference, at any rate in the aliphatic series, for the acylcholine configuration: a classical example of the principle of complementariness between substrate and active site as the basis for enzyme action. It is well known that AChE exists i…
Ontogenetic variations of some enzymes indicentrarchus labrax(Serranidae)
1989
Abstract The ontogenesis of isozyme patterns of alcohol dehydrogenase (ADH), glycerol‐3‐phosphate dehydrogenase (α‐GPDH), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), glucose‐6‐phosphate dehydrogenase (G‐6‐PD) and glucosephosphate isomer‐ase (GPI) in Dicentrarchus labrax was studied. ADH is active only in the liver of the adult; a‐GPDH is active in only two tissues in the adult: the A2 isozyme in white skeletal muscle and the B2 isozyme in the liver. Differential gene expression was found only for LDH, MDH and GPI, which have polymeric structure. The LDH, MDH and GPI isozymes 30 days after hatching were completely active and showed patterns very similar to those of the adult. Sp…
Molecular Evolution of Lactate Dehydrogenase in the Developing Nervous Tissue*
1964
Publisher Summary This chapter describes both electrophoretic and catalytic studies on lactate dehydrogenase (LDH) in the developing brain. It has been found that the enzyme exhibits at birth a composition that gradually changes to attain the final pattern observed in the adult. The neurochemical findings on LDH isozymes parallel the rapid growth in the first days after birth. Isozyme E, which is not present in detectable amounts 2 days after birth, represents 15% of the enzyme on the 22nd day. Similarly, the percentage decrease of isozyme B is quite steep at the beginning. Nevertheless, the final pattern is attained only at the end of the 2nd month that is, when the cerebral cortex is full…
Genetic diversity in theCentaurea cinerariagroup (Compositae) in Sicily using isozymes
2006
Abstract The genetic diversity of seven taxa endemic to Sicily, C. cineraria, C. busambarensis, C. ucriae subsp. ucriae, C. ucriae subsp. umbrosa, C. todari, C. erycina and C. saccensis, from 11 localities was investigated using isozymes. Eight loci from five enzyme systems (IDH, MDH, PGD, PGM and PGI) were examined. A total of 19 alleles were identified, some rare and two of them exclusive to different populations. The allelic frequencies and the genetic variability values for each population were calculated. On the whole, the genetic diversity, i.e., average polymorphism (P) = 0.41, average number of alleles per locus (A) = 1.75, Nei's gene diversity (H) = 0.18, is moderate, with the high…
Untersuchungen zur Aktivit�tskinetik des Isoenzymes CK-MB im Serum nach Myokardinfarkt
1978
We investigated the activity kinetics of CK-total and CK-MB in 83 patients with proven myocardial infarctions. Serial serum samples were taken at intervals of 2--6 h. The activity of isoenzym CK-MB was determined by means of the immunological inhibition method. CK-MB activity was determined in all patients. The mean peak activity of CK-MB was 65 U/l (range: 9-241 U/l). At the time of peak CK-MB activity the mean percentage CK-MB activity was 13.2% (range: 3.4--21.7%). The CK-MB activity reached its peak at 17.4 h (range: 3.0--32.5 h) after the onset of retrosternal pain. This is 1.4 h after peak CK-total activity. The mean disappearance rate constant for CK-MB (n = 31) was found to be 9.3 X…