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.
Roberts MC, Kidder DE, Hill FW.Two enzymes having lactase activity are present in the equine small intestine. The first, the digestive enzyme, neutral beta-galactosidase, declines in activity from birth to three years, disappearing completely between 3 and 4 years of age. The other, the soluble lysosomal enzyme, acid beta-galactosidase, having affinity for lactose and a synthetic beta-galactoside, shows a decrease in activity in the first three months of life and thereafter varies little in activity and represents the lactase enzyme in the adult horse. This pattern may parallel the development of lactase activity in many ot...
Creutz C, Sutin N.The kinetics of the reduction of horseheart ferricytochrome c by sodium dithionite (phosphate buffer-sodium chloride; pH 6.5, mu = 1.0, 25 degrees ) features two reaction pathways; one with the rate constant k(3) = 1.17 x 10(4) M(-1) sec(-1), the other with the rate constant k(1)k(2)/k(-1) = 6.0 x 10(4) M(-1) sec(-1). These pathways are interpreted in terms of remote attack (possibly by way of the exposed edge of the porphyrin system) and adjacent attack (requiring the opening of the heme crevice). The limiting rate for the adjacent pathway (k(1) = 30 sec(-1)) is in good agreement with the rat...
Oh R, Tamaoki BI.The microsomal fraction (10 000–105 000 × g precipitate) of equine testes was fractionated into the smooth- and the rough-surfaced microsomal subfractions by a sucrose density-gradient centrifugation in the presence of CsCl. The validity of this fractionating procedure was confirmed by electron microscopic examination and also by chemical analysis of the RNA contents in these subfractions. The aromatizing enzyme system (19-hydroxylase and aromatase) which was concentrated in the microsomal fractions among the organellae was found to be localized in the smoothsurfaced microsomal fraction. Th...
Smith JE, Kiefer S, Lee M.1. Reduced glutathione regeneration rates as measured in erythro- cytes of ten horses were considerably lower than rates reported in human and sheep erythrocytes.
2. Theactivityofenzymesinvolvedinreducedglutathioneregenerationwas at least three times the observed reduction rate.
3. Despitehighglucose-6-phosphatedehydrogenaseactivity,equineerythro- cytes could not adequately accelerate the hexose monophosphate pathway.
4. Activities of enzymes involved in regulating the glycolytie pathway were less than 5/~moles/min per g hemoglobin; of other glycolytic enzymes greater than 10/~moles/min per...
Brunel C, Cathala G.1. Alkaline phosphatases (orthophosphoric monoester phosphohydrolase, EC 3.1.3.1) from brain, kidney, liver, bone, lung and spleen, which are not very sensitive to l-phenylalanine, are strongly inhibited by imidazole, whereas the placental and intestinal enzymes, which are very sensitive to l-phenylalanine, are only slightly affected. This is a new possibility for distinguishing the alkaline phosphatase isoenzymes.
2. The inhibition is apparently of an uncompetitive type, suggesting that the inhibitor interacts with the ES complex to form an EIS complex.
3. Histidine acts upon all enzyme...
Kovár J, Dürrová E, Skurský L.The interactions of three groups of probes (berberine alkaloids, tricyclic psychopharmaca and acridine derivatives) with isoenzymes of horse liver alcohol dehydrogenase and with rat liver alcohol dehydrogenase have been examined. These compounds inhibit the activity of the EE isoenzyme of horse liver alcohol dehydrogenase but differ in their behaviour towards the steroid-active enzymes (i.e. the ES isoenzyme of horse liver alcohol dehydrognase and alcohol dehydrogenase from rat liver): psychopharmaca inhibit, acridines activate and berberines do not bind. The ligands differ also in their influ...
Ellerbrock RE, Podico G, Scoggin KE, Ball BA, Carossino M, Canisso IF.The expression pattern and distribution of sex steroid receptors and steroidogenic enzymes during development of the equine accessory sex glands has not previously been described. We hypothesized that equine steroidogenic enzyme and sex steroid receptor expression is dependent on reproductive status. Accessory sex glands were harvested from mature stallions, pre-pubertal colts, geldings, and fetuses. Expression of mRNA for estrogen receptor 1 (ESR1), estrogen receptor 2 (ESR2), androgen receptor (AR), 3β-Hydroxysteroid dehydrogenase/Δ5-4 isomerase (3βHSD), P450,17α hydroxylase, 17-20 lyase...
Delvescovo B, Tomlinson J, DeNotta S, Hodge E, Bookbinder L, Mohammed HO, Divers TJ.Serum biochemistry results and presence of fibrosis on liver biopsies are frequently used as prognostic indicators in horses with liver dysfunction. The objective of this retrospective multicenter study was to determine if the magnitude of abnormal liver specific biochemical tests such as bile acids (BA), direct bilirubin and gamma-glutamyltransferase (GGT), or the presence of fibrosis reported on liver biopsies was associated with prognosis in horses with liver dysfunction. Eighty-two horses older than one year, examined at four referral hospitals in the eastern United States, with BA values ...
Wunderlich G, Bull M, Ross T, Rose M, Chapman B.The equine gastrointestinal tract is a self-sufficient fermentation system, housing a complex microbial consortium that acts synergistically and independently to break down complex lignocellulolytic material that enters the equine gut. Despite being strict herbivores, equids such as horses and zebras lack the diversity of enzymes needed to completely break down plant tissue, instead relying on their resident microbes to carry out fibrolysis to yield vital energy sources such as short chain fatty acids. The bulk of equine digestion occurs in the large intestine, where digesta is fermented for 3...
Ponthier J, Franck T, Detilleux J, Mottart E, Serteyn D, Deleuze S.Despite improvement of techniques, semen of 20% of stallions remains unfreezable. Recent studies focused on the impact of reactive oxygen species and oxidant enzymes on semen characteristics. Myeloperoxidase (MPO) is a pro-oxidant enzyme contained in and released by neutrophils during degranulation or after cell lysis. It is responsible for the formation of hypochlorous acid, a strong oxidant agent, which could damage spermatozoa. The aim of this study was to determine the relation between MPO concentration and characteristics of frozen semen from stallions. Thirty-five straws from different s...
May SA, Hooke RE, Lees P.There is increasing evidence that the proteoglycan-degrading neutral metalloproteinase, stromelysin, is a key enzyme in the pathogenesis of osteoarthrosis. Equine synovial lining cells were stimulated in vitro to produce stromelysin, and phenylbutazone, flunixin, betamethasone, sodium hyaluronate and polysulphated glycosaminoglycan (PSGAG) were tested for their ability to inhibit the action of this enzyme on 14C-labelled casein substrate. Only PSGAG possessed inhibitory activity at concentrations likely to be achieved therapeutically in the equine fetlock joint.
Higgins AJ, Lees P.Arachidonic acid is a polyunsaturated fatty acid covalently bound in esterified form in the cell membranes of most body cells. Following irritation or injury, arachidonic acid is released and oxygenated by enzyme systems leading to the formation of an important group of inflammatory mediators, the eicosanoids. It is now recognised that eicosanoid release is fundamental to the inflammatory process. For example, the prostaglandins and other prostanoids, products of the cyclooxygenase enzyme pathway, have potent inflammatory properties and prostaglandin E2 is readily detectable in equine acute in...
Méténier L, Kaminski M.Immunochemical and enzymatic analyses of horse serum carboxylesterase were carried out with respect to the existence of a silent gene. Sera with positive phenotypic expression of esterase, both heterozygotes and presumed homozygotes, were compared with:--sera with positive phenotypic expression but genotypically +/O;--sera with a negative phenotypic expression, i. e. genotypically O/O;--sera of natural +/O "hemi-zygotes": mules (donkey lacking the esterase);--positive sera heated at 60 degrees C;--positive sera after specific inhibition of enzymatic activity. Titration by immunocompetition has...
Knych HK, McKemie DS, Kass PH, Stanley SD, Blea J.Ketoprofen is an anti-inflammatory drug that is commonly administered to racehorses for the alleviation of musculoskeletal pain and inflammation. This study represents a comprehensive examination of the metabolism (in vivo and in vitro), pharmacokinetics and ex vivo pharmacodynamics, of ketoprofen in horses. The in vitro metabolism as well as specific enzymes responsible for metabolism was determined by incubating liver microsomes and recombinant CYP450 and UGT enzymes with ketoprofen. For the in vivo portion, 15 horses were administered a single intravenous dose of 2.2-mg/kg ketoprofen. Blood...
Weng Q, Tanaka Y, Taniyama H, Tsunoda N, Nambo Y, Watanabe G, Taya K.To elucidate the relationship between steroidogenic hormones and developing adrenal glands, we investigated the immunolocalization of steroidogenic enzymes in equine fetal adrenal glands during mid-late gestation. Fetal adrenal glands were obtained from three horses at 217, 225 and 235 days of gestation. Steroidogenic enzymes were immunolocalized using polyclonal antisera raised against bovine adrenal cholesterol side-chain cleavage cytochrome P450 (P450scc), human placental 3beta-hydroxysteroid dehydrogenase (3betaHSD), porcine testicular 17alpha-hydroxylase cytochrome P450 (P450c17) and huma...
Hay MF, Allen WR, Lewis IM.Graafian follicles of various sizes obtained from mares at different stages of the oestrous cycle were examined histologically and histochemically for delta5-3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity and related enzymes. The 3beta-HSD activity was not found in the theca interna of any follicles but was present in the membrana granulosa of well-vascularized large follicles in the late luteal phase of the cycle and at oestrus. These findings indicate that pregnenolone cannot be converted into progesterone in the theca interna. It is suggested that this conversion occurs in the memb...
Salazar P, Graham JK, Parrish JJ, Susko-Parrish J, Squires EL.A spectrophotometric assay was developed to measure the amount of esterase released from stallion spermatozoa. This assay was used to determine the percentages of capacitated stallion spermatozoa, determined by the ability of spermatozoa to undergo an acrosome reaction and release esterase in response to a lysophosphatidylcholine challenge, for spermatozoa incubated under conditions to increase intracellular calcium and cAMP. Incubation with 100 nmol calcium ionophore A23187 l(-1) induced 66% of stallion spermatozoa to capacitate after 60 min of incubation at 37 degrees C. Subsequent experimen...
Krzywanek H, Mohr E, Mill J, Scharpenack M.Until the age of about 2 years, trotters normally grow up on pasture without any kind of training. In the stud farm Lindenhof (Templin, Germany), however, these first 2 years are used for a special fitness training for the young animals: 2-3 times a week, a group of the yearlings is forced to run a distance of about 1700 m on a track at an average speed of up to 10 m/s. Until now, little was known about changes of blood parameters which may occur during such special exercise. This study therefore investigated the activity of selected serum enzymes (aspartate-amino-transferase (AST), alanine-am...
Lochner F, Sherban DG, Sangiah S, Mauromoustakos A.Using a modified bovine milk enzyme kinetic assay, xanthine oxidase activity of serum collected from 34 adult, healthy horses of both sexes was determined. Enzyme activity varied from 0 to 126 mU litre-1 with a mean of 44.95 +/- 21.05 mU litre-1. The optimal pH and temperature for maximal activity were 7.8 and 28 degrees C, respectively. Freezing the serum for four days at -70 degrees C did not destroy the enzyme activity. Various doses (25, 50 and 75 micrograms kg-1, intraperitoneally) of endotoxin (lipopolysaccharide D1 Escherichia coli O26:B6) previously known to have caused moderate to sev...
Talluri TR, Mal G, Ravi SK.To investigate various biochemical components of seminal plasma in Marwari stallions and Poitou Jacks and to find out their correlation with that of the seminal characteristics. Methods: In this study, semen was collected from six Marwari stallions and six Poitou jacks aged from 4 to 6 years and with known fertility status. The semen collection from the stallions were collected during the breeding season, i.e., between the months of April and June. From the collected semen ejaculates, we estimated the values of some biochemical components, viz., total protein content, total lipid content, and ...
Amaral A, Cebola N, Szóstek-Mioduchowska A, Rebordão MR, Kordowitzki P, Skarzynski D, Ferreira-Dias G.Myeloperoxidase is an enzyme released by neutrophils when neutrophil extracellular traps (NETs) are formed. Besides myeloperoxidase activity against pathogens, it was also linked to many diseases, including inflammatory and fibrotic ones. Endometrosis is a fibrotic disease of the mare endometrium, with a large impact on their fertility, where myeloperoxidase was shown to induce fibrosis. Noscapine is an alkaloid with a low toxicity, that has been studied as an anti-cancer drug, and more recently as an anti-fibrotic molecule. This work aims to evaluate noscapine inhibition of collagen type 1 (C...
Beretta C, Garavaglia G, Cavalli M.We report on the inhibitory activity of the NSAIDs meloxicam, carprofen, phenylbutazone and flunixin, on blood cyclooxygenases in the horse using in vitro enzyme-linked assays. As expected, comparison of IC50 indicated that meloxicam and carprofen are more selective inhibitors of COX-2 than phenylbutazone and flunixin; meloxicam was the most advantageous for horses of four NSAIDs examined. However at IC80, phenylbutazone (+134.4%) and flunixin (+29.7%) had greater COX-2 selectivity than at IC50, and meloxicam (-41.2%) and carprofen (-12.9%) had lower COX-2 selectivity than at IC50. We therefor...
Deriusheva SE, Loginova IuA, Chiriaeva OG, Iasinetskaia NI, Efimov AM.Restriction endonuclease in situ digestion of metaphase chromosomes gives an opportunity to reveal strips with different structure within GC-rich pericentric heterochromatin of the domestic horse and the wild Przewalski horse. Blocks of heterochromatin, which are insensitive to HaeIII and brightly stained with chromomycin A3 after restriction enzyme digestion, are localized on the border with euchromatin in the majority of chromosomes of Equus caballus and E. przewalskii. In contrast to chromosome 5 of E. caballus, acrocentric chromosomes of E. prezewalskii which are homologous to this chromos...
Peng S, Magdesian KG, Dowd J, Blea J, Carpenter R, Ho W, Finno CJ.Increases in serum gamma-glutamyltransferase (GGT) activity have been reported in Thoroughbred (TB) racehorses and associated with maladaptation to training but the underlying etiology remains unknown. Objective: Classify the etiology of high GGT syndrome in racing TBs by assessment of pancreatic enzymes, vitamin E concentrations, and both a candidate gene and whole genome association study. We hypothesized that a genetic variant resulting in antioxidant insufficiency or pancreatic dysfunction would be responsible for high GGT syndrome in TBs. Methods: A total of 138 California racing TBs. Amy...
Krueger CR, Ruple-Czerniak A, Hackett ES.In horses undergoing celiotomy for acute gastrointestinal pain, identification of variables correlating with lesion severity and location, and survival provide veterinarians and owners with information that aids in making informed decisions regarding appropriate treatment. Muscle enzyme activity is often increased in horses undergoing celiotomy for acute gastrointestinal pain and it is not known if muscle enzyme activity increase is specific to lesion type or impacts prognosis for survival. The objective of this study was to evaluate the relationship of pre-operative increase in muscle enzyme ...
Hales EN, Habib H, Favro G, Katzman S, Sakai RR, Marquardt S, Bordbari MH, Ming-Whitfield B, Peterson J, Dahlgren AR, Rivas V, Ramirez CA, Peng S....Equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM) is an inherited neurodegenerative disorder associated with a vitamin E deficiency within the first year of life. Vitamin E consists of 8 isoforms metabolized by the CYP4F2 enzyme. No antemortem diagnostic test currently exists for eNAD/EDM. Objective: Based on the association of α-tocopherol deficiency with the development of eNAD/EDM, we hypothesized that the rate of α-tocopherol, but not γ-tocopherol or tocotrienol metabolism, would be increased in eNAD/EDM-affected horses. Methods: Vitamin E metabolism: Proof...
Choi MH, Kim JY, Chung BC.A highly specific method is described for measuring the testosterone:epitestosterone ratio in equine urine by gas chromatography-mass spectrometry (GC-MS) with stable isotope internal standards. The procedure was based on Serdolit Pad-1 resin extraction, enzymatic hydrolysis, and chemical derivatisation prior to instrumental analysis. The mixed derivatives, 3-trimethylsilyl-17-pentafluorophenyldimethylsilyl ether (3-TMS-17-flophemesyl) testosterone and epitestosterone, were found to have excellent analytical properties. The specificity of the derivatisation method exploits a unique feature of ...
Zobel G, Kolb FE.Acid phosphatase of erythrocytes of several species was investigated, with three isozymes having been recorded from swine (three types), three (two types) from horse, four (one type) from dog, two (two types) from cat, two (three types) from duck, and two (one type) from fowl. The Michaelis constant of the enzyme varied between 3.5 and 5 X 10(-4) M for the species involved. The species, however, differed slightly for the optimum pH of the enzyme. The average enzymatic activities were (5.68 +/- 0.42 for dog, 4.46 +/- 1.0 for horse, 3.8 +/- 0.24 for swine, 3.72 for cat, 2.5 +/- 0.62 for duck, an...
Fugler LA, Eades SC, Moore RM, Koch CE, Keowen ML.To establish an in vivo method for matrix metalloproteinase (MMP)-2 and MMP-9 induction in horses via IV administration of lipopolysaccharide (LPS) and to evaluate the ability of doxycycline, oxytetracycline, flunixin meglumine, and pentoxifylline to inhibit equine MMP-2 and MMP-9 production. Methods: 29 adult horses of various ages and breeds and either sex. Methods: In part 1, horses received an IV administration of LPS (n = 5) or saline (0.9% NaCl) solution (5). Venous blood samples were collected before and at specified times for 24 hours after infusion. Plasma was harvested and analyzed f...
Carver DA, Ball BA.Previous studies have demonstrated a detrimental effect of seminal plasma on the maintenance of motility of cooled equine spermatozoa; however, the mechanism for the adverse effect of seminal plasma during cooled storage remains undetermined. In goats, a glycoprotein component of bulbourethral gland secretion contains lipase activity that is detrimental to sperm motility when stored in skim milk-based extenders. The objective of the current study was to determine the amount of lipase activity in stallion seminal plasma and to determine the effect of added lipase on spermatozoal motility during...
Magnuson NS, Perryman LE, Suttle DP, Robinson JL, Mason PH, Marta KM.In an attempt to determine the metabolic defect causing severe combined immunodeficiency (SCID) in horses in which altered purine metabolism has been observed, various parameters of purine and pyrimidine metabolism were evaluated. The activities of nine purine enzymes (adenosine kinase, purine nucleoside phosphorylase, deoxyadenosine kinase, deoxycytidine kinase, 5'-nucleotidase, AMP deaminase, hypoxanthine-guanine phosphoribosyl transferase, and adenine phosphoribosyl transferase were measured in fibroblasts. All activities determined for SCID horses were normal. Uptake of 10 microM adenosine...
Auer DE, Ng JC, Seawright AA.Polymorphonuclear leukocytes (PMNLs) were isolated from an inflammatory exudate induced in the intercarpal joints of horses by an administration of carrageenin. Their superoxide production at rest and following stimulation with either serum-treated zymosan (STZ) or phorbol myristate acetate (PMA) was measured by cytochrome-c reduction. Stimulation of the cells increased the cytochrome-c reduction 10-15 times that of resting cells. The maxima were 20 nmol of reduced cytochrome-c per 10(6) cells per ml at 120 min (STZ) and 35 nmol of reduced cytochrome-c per 10(6) cells per ml at 60 min (PMA). T...
van den Hoven R, Meijer AE, Wensing T, Breukink HJ.Gluteal muscle specimens were taken from 4 horses. From 1 of the 4 gluteal muscles, serial sections were prepared. Individual muscle fibers were identified and studied, using photomicrographs of sections stained by different enzyme histochemical methods. In specimens in which cytoplasmic soluble enzymes were studied, use was made of the semi-permeable membrane technique to hamper enzyme diffusion into reaction fluids. Enzymes involved in glycogenolysis, glycolysis, the tricarboxylic acid cycle, synthesis of reduced nicotinamide adenine dinucleotide phosphate, the pentose phosphate cycle, the a...
Noonan NE.Adult female dogs or pony mares were subjected to a nonlethal dose of CCl4 (0.5 ml/kg of body weight). Amounts of several plasma enzymes thought to be indicative of hepatic disease were monitored. Plasma enzymes alanine aminotransferase, aspartate aminotransferase (AST), alkaline phosphatase (ALP), arginase, gamma-glutamyltransferase (GGT), and iditol dehydrogenase (ID), as well as total plasma bilirubin, were determined in these animals before and after the administration of the CCl4. In the dog, GGT was not significantly increased, whereas ALP values were increased during days 1 to 6. In the...
Tomić S, Sesartić L, Tomasić J.1. 14C-labelled methyl 2,6-di-O-pivaloyl-alpha-D-glucopyranoside (1) was used as a substrate for esterases from rabbit, guinea pig, mouse, donkey, pig, horse, sheep and human sera. 2. Stepwise de-esterification of the diester substrate 1 occurred with rabbit, guinea pig and mouse serum. Data on time-course experiments and kinetic data are reported. 3. The use of donkey, pig, horse, sheep and human serum led to the migration of the 2-O-pivaloyl group in substrate 1 to the position 4- in the sugar molecule, followed by stepwise de-esterifications of both 1 and the newly formed methyl 4,6-di-O-pi...
