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Topic:Enzymes
Enzymes are biological catalysts that facilitate biochemical reactions in horses by lowering the activation energy required for these processes. They are involved in various physiological functions, including digestion, metabolism, and cellular repair. Common enzymes in equine biology include amylase, lipase, and lactate dehydrogenase, each playing a specific role in the breakdown of nutrients and energy production. The activity and concentration of these enzymes can vary in response to different physiological and pathological conditions, serving as potential indicators in veterinary diagnostics. This page compiles peer-reviewed research studies and scholarly articles that explore the function, regulation, and clinical implications of enzymes in equine health.
Metabolic adaptation to fat-supplemented diet by the thoroughbred horse. Following 10 weeks of fat supplementation a group of aerobically trained thoroughbred horses exhibited a significant decrease in postprandial plasma triacylglycerol concentration. This decrease was associated with a mean 50% increase in plasma total lipase activity following pentosan polysulfate administration and an increase in postprandial plasma cholesterol concentration. A significant increase in the activity of muscle citrate synthase (EC 4.1.3.7), expressed as a ratio to the total fractional area occupied by type I and type IIa muscle fibres, was also observed. No significant change in t...
In vitro comparison of cytochrome P450-mediated metabolic activities in human, dog, cat, and horse. As domestic animals such as cat, horse, and dog increasingly become the clinical targets for drug discovery programs, the need to understand how these animals metabolize xenobiotics becomes more important. In the present study, substrates and inhibitors that were reported to be selective for particular P450 isozymes were used as probes to study in vitro metabolism in horse, dog, cat, and human liver microsomes. Seven selective catalytic activity markers for cytochrome P450-mediated reactions were measured: phenacetin O-deethylase (P4501A1/2), coumarin 7-hydroxylase (P4502A6), tolbutamide hydro...
IL-1 beta induces the degradation of equine articular cartilage by a mechanism that is not mediated by nitric oxide. Proteoglycan degradation was induced in young equine articular cartilage explants cultured for eight days in the presence of 50 ng/ml recombinant human interleukin-1 beta. Degradation was initiated after 6 hours of exposure to the cytokine. This was accompanied by an induction of nitric oxide synthesis and a decrease in the incorporation of [36S]sulphate into the glycosaminoglycan chains of proteoglycans. The addition of 1mM N-iminoethyl-L-ornithine (an inhibitor of nitric oxide synthase) to the explant cultures in the presence of rhIL-1 beta suppressed the synthesis of NO and restored proteog...
Evidence for the presence of sodium- and potassium-dependent adenosine triphosphatase alpha1 and beta1 subunit isoforms and their probable role in blastocyst expansion in the preattachment horse conceptus. The unusual hypotonicity of equine blastocyst fluid has prompted us to investigate the role of sodium- and potassium-dependent adenosine triphosphatase (Na+,K+-ATPase) in the process of fluid accumulation in the horse conceptus. Nine mares were used for the experiments. Reverse transcriptase polymerase chain reaction was conducted on two sets of five conceptuses recovered between 12 and 28 days (+/- 1 day) after ovulation. Messenger RNAs encoding the alpha1 and beta1 subunit isoforms of Na+,K+-ATPase were detected in all embryonic tissues examined. Western blot analysis showed that alpha1 and ...
[Salinomycin poisoning in a Polish stud horse]. 24 cases of salinomycin poisoning in horses occurring recently in Silesia are discussed. All of these horses, used for riding-purposes, were fed with concentrate containing 61 mg/kg salinomycin as faulty prepared by the manufacturer. Each horse received approximately two to three kilograms of this forage. All horses developed severe clinical signs of intoxication. Despite therapy eight horses died within three to six days. Ten others became recumbent and had to be euthanased. Only six horses survived. Clinical and laboratory examinations were performed and are discussed. Laboratory examination...
Hydrolysis of extracellular adenine nucleotides by equine epidydimal spermatozoa. Ectoenzymic activities capable of hydrolyzing ATP sequentially to adenosine are present on equine epidydimal spermatozoa membranes. Kinetic parameters for ATPase, ADPase and 5'-nucleotidase were obtained by analysis of progress reactions curve when ATP, ADP and AMP were supplied as initial substrates. These values are not different from those found when the substrates were supplied from the preceding reactions. Feed-forward inhibition on 5'-nucleotidase by ATP/ADP was taken into account to fit simulated data to the experimental results. None of the substrates supplied by the preceding reaction...
Glyceraldehyde 3-phosphate dehydrogenase is bound to the fibrous sheath of mammalian spermatozoa. Evidence is provided that the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase is covalently linked to the fibrous sheath. The fibrous sheath is a typical structure of mammalian spermatozoa surrounding the axoneme in the principal piece of the flagellum. More than 90% of boar sperm glyceraldehyde 3-phosphate dehydrogenase activity is sedimented after cell disintegration by centrifugation. Detergents, different salt concentrations or short term incubation with chymotrypsin do not solubilize the enzyme, whereas digestion with trypsin or elastase does. Short term incubation with trypsin...
Metabolic response in skeletal muscle fibres of standardbred trotters after racing. Histochemical and biochemical analyses were performed on muscle biopsies obtained after racing from the gluteus muscle of 18 standardbred trotters. Fibre type composition and enzyme activities varied among the horses. The percentage of type IIB fibres showed a positive correlation to the lactate dehydrogenase activity and a negative correlation to the citrate synthase activity. ATP concentrations in whole muscle after racing showed a negative correlation to both lactate and IMP concentrations. Within individual fibres, ATP concentrations varied markedly, with some type II fibres having values ...
Cellular heterogeneity in cathepsin D distribution in equine articular cartilage. The distribution of cathepsin D in normal equine growth cartilage has been examined immunocytochemically using an antiserum raised against human cathepsin D. The cross-reactivity and specificity of the antiserum for equine cathepsin D was confirmed, and its lysosomal localisation was demonstrated in horse skin fibroblasts by confocal scanning microscopy. Cultured horse chondrocytes were heterogenous in their expression of cathepsin D. Heterogeneity of distribution of the enzyme was also seen in chondrocytes in cartilage from different anatomical sites. A high level of cathepsin D was observed ...
Redox regulation of large conductance Ca(2+)-activated K+ channels in smooth muscle cells. The effects of sulfhydryl reduction/oxidation on the gating of large-conductance, Ca(2+)-activated K+ (maxi-K) channels were examined in excised patches from tracheal myocytes. Channel activity was modified by sulfhydryl redox agents applied to the cytosolic surface, but not the extracellular surface, of membrane patches. Sulfhydryl reducing agents dithiothreitol, beta-mercaptoethanol, and GSH augmented, whereas sulfhydryl oxidizing agents diamide, thimerosal, and 2,2'-dithiodipyridine inhibited, channel activity in a concentration-dependent manner. Channel stimulation by reduction and inhibit...
Carbonic anhydrase activity in different placenta types: a comparative study of pig, horse, cow, mink, rat, and human. The placenta has multiple functions, being the organ which provides oxygen and nutrients to the developing conceptus. In the placenta, the enzyme carbonic anhydrase (CA) may provide ions for exchange with Na+, K+, and Cl- in transepithelial movement of ions and fluid, as well as facilitating carbon dioxide diffusion. It can also be active in intermediary metabolism, such as gluconeogenesis, urea, and fatty acid synthesis. Placental material from pig, horse, cow, mink, rat, and human was therefore investigated, representing placenta types with variations in shape, internal architecture, and nat...
Protonophoric activity of NADH coenzyme Q reductase and ATP synthase in coupled submitochondrial particles from horse platelets. A method to prepare coupled submitochondrial particles from horse platelets is described. The method allowed us to study the protonophoric activities of both complex I and complex V following the fluorescence quenching of the monoamine 9-amino-6-chloro-2 methoxyacridine (ACMA), a probe highly sensitive to the generation of a transmembrane delta pH. We carried out a kinetic analysis of each enzyme complex studying the proton translocation and the electron transfer activities of complex I as well as the proton translocation and the ATP hydrolytic activities of complex V. A micromethod to prepare...
Structure of glycan moieties responsible for the extended circulatory life time of fetal bovine serum acetylcholinesterase and equine serum butyrylcholinesterase. Cholinesterases are serine hydrolases that can potentially be used as pretreatment drugs for organophosphate toxicity, as drugs to alleviate succinylcholine-induced apnea, and as detoxification agents for environmental toxins such as heroin and cocaine. The successful application of serum-derived cholinesterases as bioscavengers stems from their relatively long residence time in the circulation. To better understand the relationship between carbohydrate structure and the stability of cholinesterases in circulation, we determined the monosaccharide composition, the distribution of various oligo...
Enzyme immunoassay for measuring 25-hydroxyvitamin D3 in serum. We developed a rapid, competitive enzyme immunoassay (EIA) for measuring 25-hydroxyvitamin D3 [25(OH)D3] in serum. The EIA was based upon 25(OH)D3-3-hemisuccinate covalently coupled to secondary amino groups grafted onto the polystyrene surface of microtiter wells. Optimal coupling conditions were established, and we found that inclusion of 40 mumol/L chloramine T, an agent not previously described for use in coupling to these plates, resulted in both more reproducible coupling as well as more than a twofold increase in the coupling efficiency. Before EIA, 25(OH)D3 was extracted from the serum...
Structural characterisation and comparison of the native and A-states of equine lysozyme. Native state 1H NMR resonance assignments for 125 of the 129 residues of equine lysozyme have enabled measurement of the hydrogen exchange kinetics for over 60 backbone amide and three tryptophan indole hydrogen atoms in the native state. Native holo equine lysozyme hydrogen exchange protection factors are as large as 10(6), the most protected residues being located in elements of secondary structure. High exchange protection in the domain interface correlates with the binding of Ca2+ in this region. Equine lysozyme differs from most non-Ca2+ binding lysozymes in forming a highly populated par...
Characterization and mutational studies of equine infectious anemia virus dUTPase. The macrophage tropic lentivirus, equine infectious anemia virus (EIAV), encodes a dUTPase in the pol gene that is required for efficient replication in macrophages. Two naturally occurring variants of the enzyme were expressed as recombinant proteins in Escherichia coli; metal chelate affinity chromatography was used to purify histidine-tagged recombinant enzymes to greater than 80% homogeneity in a single chromatographic step. Biochemical and enzymatic analyses of these preparations suggest that this method yields dUTPase that is suitable for detailed mutational analysis. Specific activities...
Functional characterization of equine neutrophils in response to calcium ionophore A23187 and phorbol myristate acetate ex vivo. Equine neutrophils (PMN) play a critical role in inflammatory processes in horses. The objective of this study was to characterize equine PMN function ex vivo following stimulation with calcium ionophore A23187 (A23187) and phorbol myristate acetate (PMA). These stimulants trigger different branches of the PMN activation process that occurs in vivo. Equine PMN were isolated from the whole blood of six clinically normal geldings using a one-step discontinuous Percoll gradient technique. Neutrophil aggregation, degranulation, and superoxide anion production were evaluated in assay systems which ...
White muscle disease of foals. White muscle disease (nutritional myodegeneration) of foals is a peracute to subacute myodegenerative disease affecting skeletal and cardiac muscle. It is caused by a dietary deficiency of selenium and vitamin E, usually in association with predisposing factors such as a high intake of dietary unsaturated fats or unaccustomed exercise. White muscle disease has been observed in foals from birth to 1 year of age, particularly those foals born to dams fed selenium-deficient diets, during gestation. The disease in foals may present as an acute, fulminant syndrome, which is rapidly fatal, or a suba...
Biotransformation of chlorzoxazone by hepatic microsomes from humans and ten other mammalian species. The 6-hydroxylation of chlorzoxazone (CLZ) is currently being used in both in vivo and in vitro studies to quantify cytochrome P450 2E1 (CYP2E1) activity in humans. Comparatively little is known with regard to the biotransformation of this drug in other species. The NADPH-dependent biotransformation of CLZ was therefore studied using hepatic microsomes derived from humans and ten other mammalian species. In all species, 6-hydroxychlorzoxazone (6OH-CLZ) was the only metabolic product that could be identified by HPLC with ultraviolet detection. Enzyme kinetic analysis was used to characterize th...
Differential transcription of steroidogenic enzymes in the equine primary corpus luteum during diestrus and early pregnancy. In pregnant mares, eCG stimulates luteal androgen and estrogen production, increasing plasma concentrations 2- to 3-fold. To study how these changes are regulated, we examined the expression of mRNA for the steroidogenic enzymes 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), cytochrome P450 17 alpha-hydroxylase/17,20-lyase (P450 17 alpha), and cytochrome P450 aromatase (P450arom) in equine primary corpora lutea using Northern blot analyses. Three equine specific cDNAs were generated by reverse transcriptase polymerase chain reaction. When compared to human, bovine, and rat sequences, the nu...
Methods for the isolation, culture and characterisation of equine pulmonary artery endothelial cells. Equine endothelial cells were isolated from the pulmonary artery by enzymatic digestion and grown to confluency. The cells were characterised by positive immunofluorescent staining for von Willebrand factor and NADPH-diaphorase staining for nitric oxide synthase. Measurements of endothelins indicated that there were significant release rates from the cells for up to six hours. Measurements of intracellular calcium concentration showed that the application of bradykinin caused a transient increase in calcium concentration with similar characteristics to those observed in other endothelial cell ...
Fumonisins – Importance and occurence of a new group of mycotoxins. This paper describes the importance of fumonisins for human beings and animals and shows data for the occurence in food. Corn-based food samples (n = 299) purchased in the area of munich were analyzed for fumonisin content using an enzyme immunoassay.Fumonisins are mycotoxins produced byFusarium species, especially byFusarium moniliforme andFusarium proliferatum. Occurrence of fumonisins in corn and in cornbased foods and feeds has been reported from almost all over the world. In several animal species different diseases are traced back to fumonisin toxicosis. Fumonisin levels of 5-10 ppm inho...
Erythrocyte glutathione-S-transferase activity in animal species. This study was conducted to determine and compare the activities of glutathione-S-transferase (GST) in red blood cells of cattle, horses, pigs, goats, dogs, rabbits, rats and mice. The highest GST activity was found in mouse red blood cells followed by that of rats, dogs, cattle, pigs, goats and horses with the lowest activity in rabbits. There were significant differences between the GST activities from these various species. The species differences in GST activities correlate with the reported variable responses of the different species to different toxicants since erythrocyte GST plays a si...
Consideration of the optimum pH for the analysis of serum p-phenylenediamine oxidase activity in thoroughbred horses. The optimum pH for the measurement of serum p-phenylenediamine oxidase (Ox) activity was given (pH 6.6), and the relationship between serum ceruloplasmin (Cp) concentration and its Ox activity was established in healthy adult horses. In adult horses, serum antigenic Cp concentrations were measured by the single radial immunodiffusion (SRID) method with the affinity-purified antibody to equine plasma Cp and compared with its Ox activity. Efficient co-relation between Cp concentration and Ox activity in the sera (r = 0.93) and its Ox/Cp ratio were given. These results might contribute to the cal...
Skeletal muscle characteristics and metabolic response to exercise in young standardbreds. To determine whether performance capacity in a group of young trained Standardbreds is related to skeletal muscle characteristics and metabolic response to exercise. Methods: 13 clinically normal 2-year-old Standardbreds. Methods: Venous blood and middle gluteal muscle biopsy samples were obtained from each horse within 1 to 2 minutes after trotting at high speed for 1,600 m. Results: There was a positive correlation between plasma lactate and muscle glucose-6-phosphate (G-6-P) concentrations and trotting speed. There was a negative correlation between muscle adenosine triphosphate concentrati...
Total cholinesterase activity in discrete brain regions and retina of normal horses. The research evaluates cholinesterase activity across different brain regions in horses to better understand its role in neuromuscular function and how it can be affected by certain toxic exposures. Cholinesterase […]
Some parameters influencing immunoassay of human and horse myoglobins. It was noted that human and horse sera as well as human heart and skeletal muscle homogenates or extracts distinctly decrease immunoassays of purified myoglobins. The assays of homogenate and extract myoglobins could be many times increased by precipitation certain proteins with concentrated ammonium sulfate or sodium chloride. Also in homogenates and extracts incubated for several days increased assays of myoglobins were noted. The obtained results indicate that both myoglobins occur in complex with other tissue component(s).
Gelatinolytic activity in tracheal aspirates of horses with chronic obstructive pulmonary disease. The gelatinolytic activity in tracheal aspirates (TA) of horses with chronic obstructive pulmonary disease (COPD) was analyzed using SDS-PAGE-gelatin-gel electrophoresis (zymography) and compared to TAs from healthy controls. The 110-90 kD MMP-9 type gelatinase was high in symptomatic disease phases (permanent disease 0.46 +/- 0.15, p < 0.001; or intermittent disease 0.47 +/- 0.12, p < 0.001) compared to healthy controls (0.10 +/- 0.07). Similarly, the overall gelatinolytic activity, the activity in high-mw gelatinolytic bands (210-190 and 150 kD) and in proteolytically processed fragments in ...
Myoglobin oxygen dissociation by multiwavelength spectroscopy. Multiwavelength optical spectroscopy was used to determine the oxygen-binding characteristics for equine myoglobin. Oxygen-binding relationships as a function of oxygen tension were determined for temperatures of 10, 25, 35, 37, and 40 degrees C, at pH 7.0. In addition, dissociation curves were determined at 37 degrees C for pH 6.5, 7.0, and 7.5. Equilibration was achieved with a myoglobin solution, at the desired temperature and pH, and 16 oxygen-nitrogen gas mixtures of known oxygen fraction. Correction for the inevitable presence of metmyoglobin was made by using a three-component least squ...
Local electrostatic potentials in pyridoxal phosphate labelled horse heart cytochrome c. The present work shows the application of an optical label pyridoxal phosphate (PLP) for the experimental determination of local electrostatic potentials in singly substituted cytochromes c modified by pyridoxal phosphate at Lys 79 (PLP-Lys-79-cyt.c) or at Lys 86 (PLP-Lys-86-cyt.c). PLP has also been used to calculate the pKa values of all ionizable groups and the electrostatic potentials in the modified proteins and to analyse their properties. The experimental pKa values for the pyridine nitrogen and phenolic hydroxyl of the bound label were obtained from pH-dependent absorbance and fluoresc...
