THE INTERACTION OF ENZYMES AND HORMONES

PEDIATRICS ◽  
1960 ◽  
Vol 26 (3) ◽  
pp. 476-481
Author(s):  
Abraham White
Keyword(s):  
Direct Effect ◽  
Chemical Reactions ◽  
Elevated Temperatures ◽  
Enzyme System ◽  
Enzymic Activity ◽  
Hormone Interaction ◽  
Indirect Influence ◽  
Rare Exception ◽  
Hormonal Action

The majority of living forms depend for their functioning upon two classes of biocatalysts, the enzymes and the hormones. These biocatalysts permit the diverse chemical reactions of the organism to proceed at 38°C with a specificity and at rates frequently unattainable in vitro at elevated temperatures with similar reactants. The physiologic importance of enzymes and hormones is evident not only under normal circumstances, but is reflected clinically in the diverse descriptions of errors of metabolism, due to lack or deficiency of one or more enzymes, and the numerous hypo- and hyperfunctioning states resulting from imbalance of hormonal supply. Inasmuch as both enzymes and hormones function, with rare exception, to accelerate the rates of processes in cells, investigators have sought possible interrelationships and interactions of enzymes and hormones, particularly as a basis for the mechanism of hormonal action. It has seemed logical to hypothesize that hormones, while not essential for reactions to proceed but nevertheless affecting the rates of reactions, may function by altering either the concentration or activity of the prime cellular catalysts, the enzymes. This proposed influence of hormones on enzymic activity might be a primary, direct effect achieved by the hormone participating as an integral part of an enzyme system, or an indirect influence based upon the hormone altering the concentration of available enzyme and/or substrate utilized by a particular enzyme. It is the purpose of this presentation to describe a relatively few, but better defined, examples of the more direct relationships of enzymes and hormones. Five examples of enzyme-hormone interaction will be presented, based on the criterion that an effect of the hormone has been demonstrated on addition of the hormone in vitro to a purifled, or partially purified, enzyme system.

Binding of Tissue Plasminogen Activator to Vascular Grafts

1989 ◽  
Vol 61 (01) ◽  
pp. 131-136 ◽  
Author(s):  
Richard A Harvey ◽  
Hugh C Kim ◽  
Jonathan Pincus ◽  
Stanley Z Trooskin ◽  
Josiah N Wilcox ◽  
...  
Keyword(s):  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Fibrinolytic Activity ◽  
Polymer Surface ◽  
Enzymic Activity ◽  
Vascular Prostheses ◽  
Chemically Modified ◽  
Insoluble Surfactant ◽  
Tissue Plasminogen

SummaryTissue plasminogen activator labeled with radioactive iodine (125I-tPA) was immobilized on vascular prostheses chemically modified with a thin coating of water-insoluble surfactant, tridodecylmethylammonium chloride (TDM AC). Surfactant- treated Dacron, polytetrafluoroethylene (PTFE), silastic, polyethylene and polyurethane bound appreciable amounts of 125I- tPA (5-30 μg 125I-tPA/cm2). Upon exposure to human plasma, the amount of 125I-tPA bound to the surface shows an initial drop during the first hour of incubation, followed by a slower, roughly exponential release with a t½ of appoximately 75 hours. Prostheses containing bound tPA show fibrinolytic activity as measured both by lysis of clots formed in vitro, and by hydrolysis of a synthetic polypeptide substrate. Prior to incubation in plasma, tPA bound to a polymer surface has an enzymic activity similar, if not identical to that of the native enzyme in buffered solution. However, exposure to plasma causes a decrease in the fibrinolytic activity of both bound tPA and enzyme released from the surface of the polymer. These data demonstrate that surfactant-treated prostheses can bind tPA, and that these chemically modified devices can act as a slow-release drug delivery system with the potential for reducing prosthesis-induced thromboembolism.

Superoxide, Xanthine Oxidase and Platelet Reactions: Further Studies on Mechanisms by which Oxidants Influence Platelets

1981 ◽  
Vol 45 (03) ◽  
pp. 290-293 ◽  
Author(s):  
Peter H Levine ◽  
Danielle G Sladdin ◽  
Norman I Krinsky
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Xanthine Oxidase ◽  
Direct Effect ◽  
Platelet Function ◽  
Experimental Conditions ◽  
Release Reaction

SummaryIn the course of studying the effects on platelets of the oxidant species superoxide (O- 2), Of was generated by the interaction of xanthine oxidase plus xanthine. Surprisingly, gel-filtered platelets, when exposed to xanthine oxidase in the absence of xanthine substrate, were found to generate superoxide (O- 2), as determined by the reduction of added cytochrome c and by the inhibition of this reduction in the presence of superoxide dismutase.In addition to generating Of, the xanthine oxidase-treated platelets display both aggregation and evidence of the release reaction. This xanthine oxidase induced aggreagtion is not inhibited by the addition of either superoxide dismutase or cytochrome c, suggesting that it is due to either a further metabolite of O- 2, or that O- 2 itself exerts no important direct effect on platelet function under these experimental conditions. The ability of Of to modulate platelet reactions in vivo or in vitro remains in doubt, and xanthine oxidase is an unsuitable source of O- 2 in platelet studies because of its own effects on platelets.

Effect of Temperature, Velocity Gradient and I.V. Heparin on in Vitro Blood Coagulation and Platelet Aggregation

1967 ◽  
Vol 17 (01/02) ◽  
pp. 112-119 ◽  
Author(s):  
L Dintenfass ◽  
M. C Rozenberg
Keyword(s):  
Blood Coagulation ◽  
Velocity Gradient ◽  
Elevated Temperatures ◽  
Morphological Changes ◽  
Effect Of Temperature ◽  
Clotting Time ◽  
Progressive Change ◽  
Aggregation Of Platelets ◽  
Microscopic Techniques

SummaryA study of blood coagulation was carried out by observing changes in the blood viscosity of blood coagulating in the cone-in-cone viscometer. The clots were investigated by microscopic techniques.Immediately after blood is obtained by venepuncture, viscosity of blood remains constant for a certain “latent” period. The duration of this period depends not only on the intrinsic properties of the blood sample, but also on temperature and rate of shear used during blood storage. An increase of temperature decreases the clotting time ; also, an increase in the rate of shear decreases the clotting time.It is confirmed that morphological changes take place in blood coagula as a function of the velocity gradient at which such coagulation takes place. There is a progressive change from the red clot to white thrombus as the rates of shear increase. Aggregation of platelets increases as the rate of shear increases.This pattern is maintained with changes of temperature, although aggregation of platelets appears to be increased at elevated temperatures.Intravenously added heparin affects the clotting time and the aggregation of platelets in in vitro coagulation.

Angiogenic Effect of Pravastatin Alone and with Sera from Healthy and Complicated Pregnancies Studied by in vitro Vasculogenesis/Angiogenesis Assay

2021 ◽  
pp. 1-9
Author(s):  
Anita Virtanen ◽  
Outi Huttala ◽  
Kati Tihtonen ◽  
Tarja Toimela ◽  
Tuula Heinonen ◽  
...  
Keyword(s):  
Direct Effect ◽  
Late Onset ◽  
Maternal Serum ◽  
In Vitro Assay ◽  
Serum Samples ◽  
Therapeutic Concentration ◽  
Tubule Formation ◽  
Vitro Assay ◽  
Angiogenesis Assay

<b><i>Objective:</i></b> To determine the direct effect of pravastatin on angiogenesis and to study the interaction between pravastatin and maternal sera from women with early- or late-onset pre-eclampsia (PE), intrauterine growth restriction, or healthy pregnancy. <b><i>Methods:</i></b> We collected 5 maternal serum samples from each group. The effect of pravastatin on angiogenesis was assessed with and without maternal sera by quantifying tubule formation in a human-based in vitro assay. Pravastatin was added at 20, 1,000, and 8,000 ng/mL concentrations. Concentrations of angiogenic and inflammatory biomarkers in serum and in test medium after supplementation of serum alone and with pravastatin (1,000 ng/mL) were measured. <b><i>Results:</i></b> Therapeutic concentration of pravastatin (20 ng/mL) did not have significant direct effect on angiogenesis, but the highest concentrations inhibited angiogenesis. Pravastatin did not change the levels of biomarkers in the test media. There were no changes in angiogenesis when therapeutic dose of pravastatin was added with maternal sera, but there was a trend to wide individual variation towards enhanced angiogenesis, particularly in the early-onset PE group. <b><i>Conclusions:</i></b> At therapeutic concentration, pravastatin alone or with maternal sera has no significant effect on angiogenesis, but at high concentrations the effect seems to be anti-angiogenic estimated by in vitro assay.

In vitro evaluation of the direct effect of estradiol on human osteoblasts (HOB) and human mesenchymal stem cells (h-MSCs)

Injury ◽  
2006 ◽  
Vol 37 (3) ◽  
pp. S33-S42 ◽  
Author(s):  
Lucy DiSilvio ◽  
Jacqueline Jameson ◽  
Zakareya Gamie ◽  
Peter V. Giannoudis ◽  
Eleftherios Tsiridis
Keyword(s):  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
Direct Effect ◽  
Human Mesenchymal Stem Cells ◽  
Human Osteoblasts ◽  
In Vitro Evaluation

scholarly journals Localization of ferrochelatase in Plasmodium falciparum

2004 ◽  
Vol 384 (2) ◽  
pp. 429-436 ◽  
Author(s):  
Sundaramurthy VARADHARAJAN ◽  
B. K. Chandrashekar SAGAR ◽  
Pundi N. RANGARAJAN ◽  
Govindarajan PADMANABAN
Keyword(s):  
Plasmodium Falciparum ◽  
De Novo ◽  
Enzymic Activity ◽  
Malarial Parasite ◽  
Parasite Genome ◽  
Marker Proteins ◽  
Parasite Plasmodium ◽  
Theoretical Predictions ◽  
Parasite Plasmodium Falciparum

Our previous studies have demonstrated de novo haem biosynthesis in the malarial parasite (Plasmodium falciparum and P. berghei). It has also been shown that the first enzyme of the pathway is the parasite genome-coded ALA (δ-aminolaevulinate) synthase localized in the parasite mitochondrion, whereas the second enzyme, ALAD (ALA dehydratase), is accounted for by two species: one species imported from the host red blood cell into the parasite cytosol and another parasite genome-coded species in the apicoplast. In the present study, specific antibodies have been raised to PfFC (parasite genome-coded ferrochelatase), the terminal enzyme of the haem-biosynthetic pathway, using recombinant truncated protein. With the use of these antibodies as well as those against the hFC (host red cell ferrochelatase) and other marker proteins, immunofluorescence studies were performed. The results reveal that P. falciparum in culture manifests a broad distribution of hFC and a localized distribution of PfFC in the parasite. However, PfFC is not localized to the parasite mitochondrion. Immunoelectron-microscopy studies reveal that PfFC is indeed localized to the apicoplast, whereas hFC is distributed in the parasite cytoplasm. These results on the localization of PfFC are unexpected and are at variance with theoretical predictions based on leader sequence analysis. Biochemical studies using the parasite cytosolic and organellar fractions reveal that the cytosol containing hFC accounts for 80% of FC enzymic activity, whereas the organellar fraction containing PfFC accounts for the remaining 20%. Interestingly, both the isolated cytosolic and organellar fractions are capable of independent haem synthesis in vitro from [4-14C]ALA, with the cytosol being three times more efficient compared with the organellar fraction. With [2-14C]glycine, most of the haem is synthesized in the organellar fraction. Thus haem is synthesized in two independent compartments: in the cytosol, using the imported host enzymes, and in the organellar fractions, using the parasite genome-coded enzymes.

AROMATIZING ACTIVITY OF PLACENTAL MICROSOMAL FRACTIONS FROM EWES IN LATE GESTATION

1975 ◽  
Vol 65 (1) ◽  
pp. 117-125 ◽  
Author(s):  
M. R. MANN ◽  
L. B. CURET ◽  
A. E. COLAS
Keyword(s):  
Sharp Increase ◽  
Enzyme System ◽  
Hydroxysteroid Dehydrogenase ◽  
Relative Increase ◽  
Late Gestation ◽  
Domestic Sheep ◽  
Dramatic Rise ◽  
Oestradiol Production ◽  
Human Placentae

SUMMARY Placental microsomes from eight domestic sheep at 136–146 days of gestation were incubated with radioactive androstenedione, testosterone and dehydroepiandrosterone. Aromatizing activity was examined in the presence and absence of cortisol and the rates of both oestrone and oestradiol synthesis were measured. Oestrone predominated in preference to oestradiol in most of the incubations, a result opposite to that found with human placentae. The sharp increase in the rate of oestradiol production found in the 144- to 146-day-old placentae incubated with testosterone may indicate a more rapid increase of aromatizing than of 17β-hydroxysteroid dehydrogenase activity. The presence of cortisol in the mixtures did not significantly affect the placental aromatizing activity, indicating that there is no direct effect of cortisol on the enzyme system as measured in vitro. The dramatic rise of overall mean aromatizing activity from 4·86 ± 0·22 (s.e.m.) at 138–141 days of gestation to 12·96 ± 0·38 pmol/mg protein/min at 144–146 days (with a greater relative increase in the rate of oestradiol formation), suggests that changes in placental aromatizing activity may play an important role in maternal and foetal plasma oestrogen surges before ovine parturition.

scholarly journals All1371 is a polyphosphate-dependent glucokinase in Anabaena sp. PCC 7120

Microbiology ◽  
2014 ◽  
Vol 160 (12) ◽  
pp. 2807-2819 ◽  
Author(s):  
Friederike Klemke ◽  
Gabriele Beyer ◽  
Linda Sawade ◽  
Ali Saitov ◽  
Thomas Korte ◽  
...  
Keyword(s):  
Divalent Cations ◽  
Enzymic Activity ◽  
Phosphoryl Group ◽  
Nitrogen Deprivation ◽  
Ping Pong ◽  
Nucleoside Triphosphates ◽  
Anabaena Sp ◽  
Pcc 7120 ◽  
Promoter Studies

The polyphosphate glucokinases can phosphorylate glucose to glucose 6-phosphate using polyphosphate as the substrate. ORF all1371 encodes a putative polyphosphate glucokinase in the filamentous heterocyst-forming cyanobacterium Anabaena sp. PCC 7120. Here, ORF all1371 was heterologously expressed in Escherichia coli, and its purified product was characterized. Enzyme activity assays revealed that All1371 is an active polyphosphate glucokinase that can phosphorylate both glucose and mannose in the presence of divalent cations in vitro. Unlike many other polyphosphate glucokinases, for which nucleoside triphosphates (e.g. ATP or GTP) act as phosphoryl group donors, All1371 required polyphosphate to confer its enzymic activity. The enzymic reaction catalysed by All1371 followed classical Michaelis–Menten kinetics, with k cat = 48.2 s−1 at pH 7.5 and 28 °C and K M = 1.76 µM and 0.118 mM for polyphosphate and glucose, respectively. Its reaction mechanism was identified as a particular multi-substrate mechanism called the ‘bi-bi ping-pong mechanism’. Bioinformatic analyses revealed numerous polyphosphate-dependent glucokinases in heterocyst-forming cyanobacteria. Viability of an Anabaena sp. PCC 7120 mutant strain lacking all1371 was impaired under nitrogen-fixing conditions. GFP promoter studies indicate expression of all1371 under combined nitrogen deprivation. All1371 might play a substantial role in Anabaena sp. PCC 7120 under these conditions.

In vitro biosynthesis of steroid sulfates by cell-free preparations from tissues of the laying hen

1968 ◽  
Vol 46 (8) ◽  
pp. 749-757 ◽  
Author(s):  
H. R. Raud ◽  
R. Hobkirk
Keyword(s):  
Enzyme System ◽  
Laying Hen ◽  
Product Identification ◽  
Temperature Requirements ◽  
Before And After ◽  
Liver Preparation ◽  
Steroid Sulfate ◽  
In Vitro Biosynthesis ◽  
Estradiol 17Β

The sulfurylation of estrone-6,7-3H, estradiol-17β-6,7-3H, and dehydroisoandrosterone-4-14C by laying hen liver, oviduct, and vaginal preparations was investigated. Purification and product identification included ether and ethyl acetate extraction, paper chromatography, and isotope dilution, before and after hydrolysis with a sulfatase preparation.The esterifying enzymes were found in the 105 000 × g supernatants of the three tissues. The liver preparation was many times more active in steroid sulfate synthesis than the corresponding oviduct or vaginal fractions. Sulfurylation of dehydroisoandrosterone displayed the same cofactor, pH, and temperature requirements as did that of estrone and estradiol-17β. The degree of dehydroisoandrosterone sulfate synthesis was considerably lower than that of the estrogens, however. It is suggested that the laying hen possesses an enzyme system which is more efficient for the sulfurylation of estrogens than of other steroids such as dehydroisoandrosterone.

Enzyme system of Clostridium stercorarium for hydrolysis of arabinoxylan: reconstitution of the in vivo system from recombinant enzymes

Microbiology ◽  
2004 ◽  
Vol 150 (7) ◽  
pp. 2257-2266 ◽  
Author(s):  
Helmuth Adelsberger ◽  
Christian Hertel ◽  
Erich Glawischnig ◽  
Vladimir V. Zverlov ◽  
Wolfgang H. Schwarz
Keyword(s):  
Extracellular Enzymes ◽  
Enzyme System ◽  
Thermophilic Bacterium ◽  
Recombinant Enzymes ◽  
Type Mode ◽  
Complete Set ◽  
First Time ◽  
Hydrolysis Of

Four extracellular enzymes of the thermophilic bacterium Clostridium stercorarium are involved in the depolymerization of de-esterified arabinoxylan: Xyn11A, Xyn10C, Bxl3B, and Arf51B. They were identified in a collection of eight clones producing enzymes hydrolysing xylan (xynA, xynB, xynC), β-xyloside (bxlA, bxlB, bglZ) and α-arabinofuranoside (arfA, arfB). The modular enzymes Xyn11A and Xyn10C represent the major xylanases in the culture supernatant of C. stercorarium. Both hydrolyse arabinoxylan in an endo-type mode, but differ in the pattern of the oligosaccharides produced. Of the glycosidases, Bxl3B degrades xylobiose and xylooligosaccharides to xylose, and Arf51B is able to release arabinose residues from de-esterified arabinoxylan and from the oligosaccharides generated. The other glycosidases either did not attack or only marginally attacked these oligosaccharides. Significantly more xylanase and xylosidase activity was produced during growth on xylose and xylan. This is believed to be the first time that, in a single thermophilic micro-organism, the complete set of enzymes (as well as the respective genes) to completely hydrolyse de-esterified arabinoxylan to its monomeric sugar constituents, xylose and arabinose, has been identified and the enzymes produced in vivo. The active enzyme system was reconstituted in vitro from recombinant enzymes.

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