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.
Srivastava SK, Beutler E.1. Erythrocytes from normal and glucose 6-phosphate dehydrogenase-deficient humans were subjected to hydrogen peroxide diffusion to oxidize the GSH. Studies were carried out in the presence and absence of chromate to inhibit glutathione reductase and with or without the addition of glucose. 2. The GSH content of erythrocytes from other species was oxidized by subjecting them to hydrogen peroxide diffusion in the presence of chromate and glucose. 3. Chromate (1.3mm) inhibited glutathione reductase by about 80%, whereas glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, hexokin...
Leikola E, Nieminen E, Teppo AM.Human epidermis, hair, nails, and kidney as well as bovine and horses' hooves were found to contain a lipid fraction, which on thin-layer chromatography migrated slightly ahead of the cerebroside sulfate esters and gave the color reaction specific for sialic acid. This fraction was isolated from horse hoof, in which it constituted nearly half of the total lipids. The purified fraction contained sulfur, but no phosphorus. The IR spectrum revealed the presence of a sulfate group, which was also determined by the benzidine method. Thin-layer and gas-liquid chromatography of the products of acid h...
Mori M, Sakiyama Y.The histochemical distribution of some hydrolytic and oxidative enzymes in developing odontoblasts and subodontoblasts in cattle, pigs and horses has been observed in cryostat sections of teeth that have been decalcified with neutral EDTA.
Undifferentiated dental epithelium and immature odontoblasts of the bell stage tooth germ showed lower levels of enzymatic activity as compared with the well-developed tooth germ.
When the dentine matrix began to form, the young odontoblasts appeared to have a significantly positive reaction for acid phosphatase, and gradually other enzymes developed a...
Babel I, Stella RC, Prado ES.Previous experiments indicated that horse urinary kallikrein (UK) hydrolyzes salminei- e and polyarginine, a but not polylysine. This paper reports the action of UK on bradykinyl-serine, methionyllysyl-bradykinin and lysyllysyl-bradykinin.
Holmes RS, Masters CJ.Multiple forms of soluble esterase activity have been resolved in horse, sheep, ox and possum tissue extracts and sera. 2. By comparing esterase zymograms from different tissues and from different species, it is apparent that the distribution and multiplicity of esterase activity is tissue and species specific. 3. By means of substrate and inhibitor studies, the esterase multiple forms have been characterized into four main classes : carboxylesterases, arylesterases, acetylesterases, and cholinesterases. Each of these can be considered as an isoenzymic group. 4. Evidence is presented for furth...
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...
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...
Yamamoto M, Yamamoto I, Tanaka Y, Sugano M.1. A method for the purification of horse serum lecithin:cholesterol acyltransferase has been established. 2. The method involves the adsorption of the enzyme from diluted horse serum on DEAE-Sephadex A-50, (NH4)2SO4 fractionation, 1-butanol treatment, and chromatographic techniques of DEAE-Sepharose CL-6B, DEAE-Sephadex A-50, Affi-Gel blue and hydroxylapatite. 3. The resultant enzyme preparation essentially formed a single main band when subjected to polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. 4. The final purification of the enzyme was 20,000-fold with 7% yi...
Jones S, Blackmore DJ.The distribution of the isoenzymes of aspartate aminotransferase (AST, E.C. 2.6.1.1.) in equine tissues has been studied to ascertain whether the organ of origin may be identified when the total AST activity of serum is raised. Most tissues contain 3 isoenzymes of cytoplasmic origin (cAST) with isoelectric points of 5.6, 5.7 and 5.9, and one isoenzyme of mitochondrial (mAST) origin with an isoelectric point of 9. Serum from horses with azoturia contained an additional cytoplasmic subform with an isoelectric point of 5.8. This form could not be generated by ageing, freezing and thawing or bindi...
Owen M, Ferjak EN, Cavinder CA, McCarty KJ, Yankey KC, Hart CG, Burnett DD, Dinh T, Lemley CO.The objective of this study was to determine the activity of steroid- and eicosanoid-metabolizing enzymes in horses with varying BCSs. The BCSs of twenty non-pregnant, anoestrous mares were determined prior to euthanasia, and tissue samples were collected from the liver, kidney, adrenal gland, ovary and endometrium. Cytochrome P450 1A (CYP1A), 2C (CYP2C), 3A (CYP3A) and uridine 5'-diphospho-glucuronosyltransferase (UGT) activities were determined using luminogenic substrates. The MIXED procedure of SAS was used to test the effect of BCS on enzyme activity and differences between tissues. Activ...
Pham HC, Lasserre B, Tronche P, Couquelet J, Dossou-Gbete V, Palhares de Miranda AL.The effects of 3-dimethylamino 5-(2',6'-dichlorobenzylidene) 6-methyl (4H)-pyridazine (PC 89) on the biosynthesis of PG I2 and TX A2 using horse aorta and horse platelet microsomes as sources of enzymes and arachidonic acid as substrate, were investigated. PC 89 (1.10(-6) M- 1.10(-3) M) dose-dependently - enhanced the biosynthesis of PG I2: the AD50 was 6.8 X 10(-6) M +/- 1.2 X 10(-9) M, the Vmax did not vary significantly with concentrations: PC 89 increased the affinity of enzyme for substrate - but inhibited TX A2 biosynthesis (ID50 = 3.31 X 10(-3) M +/- 4.8 X 10(-7) M): this inhibiting act...
Grulke S, Gangl M, Deby-Dupont G, Caudron I, Deby C, Serteyn D.Gastrointestinal disorders in horses leading to endotoxic shock could have further consequences on other splanchnic organs such as the pancreas, as can be seen in humans suffering from septic shock. In this study, the range of enzymatically active trypsin (EAT) in healthy horses was established and is similar to the range observed in healthy humans. EAT values were determined in horses with acute abdominal crises on admission as well as during anaesthesia and in the postoperative phase. A significant increase in plasma EAT was found in 59% of the horses with surgical colic when compared to our...
Moura J, Simplício AL.This study describes an electrophoretically mediated microanalysis method, suitable for the preclinical evaluation of the hydrolysis of ester drugs by the serum of different animals and for further characterization of human-animal correlation. Dog, cat, cow, horse, sheep, rat and human serum were diluted (25%) in the appropriate buffer and replaced the enzyme solution usually used in electrophoretically mediated microanalysis methods for the study of enzyme kinetics. They were then compared in terms of the ability to hydrolyze acetylthiocholine and butyrylthiocholine (0.25 mM) by in-capillary ...
Wynn MAA, Ball BA, Legacki E, Conley A, Loux S, May J, Esteller-Vico A, Stanley S, Scoggin K, Squires E, Troedsson M.In the latter half of gestation in the mare, progesterone concentrations decline to near undetectable levels while other 5α-reduced pregnanes are elevated. Of these, 5α-dihydroprogesterone and allopregnanolone have been reported to have important roles in either pregnancy maintenance or fetal quiescence. During this time, the placenta is necessary for pregnane metabolism, with the enzyme 5α-reductase being required for the conversion of progesterone to 5α-dihydroprogesterone. The objectives of this study were to assess the effects of a 5α-reductase inhibitor, dutasteride on pregnane metab...
Casella S, Piccione D, Ielati S, Bocchino EG, Piccione G.The aim of this study was to assess the anion transport in equine erythrocytes through the measurement of the sulfate uptake operating from band 3 using different experimental temperatures and buffer solutions. Blood samples of six clinically healthy horses were collected via jugular vein puncture, and an emochrome-citometric examination was performed. The blood was divided into four aliquots and by centrifugation and aspiration the plasma and buffy coat were carefully discarded. The red blood cells were washed with an isosmotic medium and centrifuged. The obtained cell suspensions were incuba...
Dietz HH.Diagnostic tests in horses showing signs of gastrointestinal diseases are reviewed. The use of rectal exploration is emphasized, and paracentesis as a diagnostic aid is mentioned. Special attention is given to the absorption tests as they are easy to conduct and give a relative measure of the absorptive capability of the intestinal epithelium. Glucose, D(+)-xylose and carbohydrate digestion-absorption tests are compared, and the D(+)-xylose absorption test is preferred because of the univocal curve of absorption (see Figure 1 and 2). The absorption curve in a horse suffering from alimentary ly...
Kaminski M.The detection of the recessive null allele of horse serum esterase (Es) is possible in heterozygotes Es+/EsO which by starch gel electrophoresis appear like homozygotes Es+/Es+. Two methods are proposed, the titration of enzymatic activity of esterase and the immunochemical titration of esterase as antigen. These methods can be applied to solve the cases of suspect parentage or in population studies.
Harvey JW, Kaneko JJ.Glutathione reductase (GR) was studied in erythrocytes of horses, cats, dogs, and man. Glutathione reductase activity was measured in hemolysates with and without preincubation of hemolysates with flavinadenine dinucleotide. The percentage saturation of GR apoenzyme with cofactor (flavin-adenine dinucleotide) was lower in cats and dogs than in horses or man. The greatest amount of inactive apoenzyme was in feline erythrocytes. Total GR activity listed in order by species is cat greater than man greater than dog greater than horse. Kinetic constants for oxidized glutathione and reduced nicotina...
Basova NE, Kormilitsin BN, Perchenok AIu, Rozengart EV, Saakov VS, Suvorov AA.There was studied action of aliphatic alcohols (ethanol, propanol, isopropanol, n-butanol, isobutanol, secbutanol, tretbetanol) and pH on various kinds of reactional capability the serum cholinesterase. At the alcohols-affected inhibition of the cholinesterase hydrolytic activity, the determining role was played not the total number carbon atoms in the alcohol molecule, but by the "effective length" of the carbohydrate chain. The fact that the presence of alcohols did not affect parameters of the reverse cholinesterase inhibition with onium ions tetramethylammonium and choline allows suggestin...
Yamada S, Suruga K, Ogawa M, Hama T, Satoh T, Kawachi R, Nishio T, Oku T.The appearance of NO2- reducing activity of cytochrome c (Cyt c) upon heat denaturation was investigated with equine heart Cyt c. Denatured equine heart Cyt c (dCyt c), which was treated at 100 degrees C for 30 min, had NO2- reducing activity in the presence of dithionite and methylviologen in an aqueous solution under anaerobic conditions. In contrast, hemoglobin and myoglobin had no such activity under the same conditions. Using spectroscopic methods, we found that the appearance of this activity in the Cyt c was due to the following intramolecular changes: unfolding of the peptide chain, ex...
Yee S, Peyton DH.The redistribution of the initially-formed myoglobin heme-insertion isomers from the initially formed 50/50 mixture to the equilibrium ratio of 90/10 has long been assumed to occur by one of two mechanisms, both of which require the rupture of the heme iron-protein bond (La Mar, G.N., Toi, H. and Krishnamoorthi, K. (1984) J. Am. Chem. Soc. 106, 6395-6401). In this study we compared the use of nuclear magnetic resonance and optical spectroscopic techniques as methods for studying the reorientation of heme within myoglobin. We found that kinetics determinations of the heme insertion isomer redis...
Makhaeva GF, Shataeva GA, Iankovskaia VL, Fetisov VI, Loshadkin NA.The interaction of human erythrocyte acetylcholinesterase, horse serum butyrylcholinesterase and rat liver carboxylesterase with insecticides (RO)2P(O)SCH(COOEt)SP(O)(OR)2 (I) and (RO)2P(O)SCH(COOEt)OP(S)(OR)2 (II) was studied. The type I and II compounds were not hydrolyzed by carboxylesterase and inhibited the esterases irreversibly. A complex pattern of inhibition of acetylcholinesterase and butyrylcholinesterase by these compounds was caused by kinetically-manifested formation of an enzyme-inhibitor complex. The compounds I and II were more selective towards butyrylcholinesterase than towa...
Hubbard CD, Shoupe TS.A transient phase for the hydrolysis of indophenyl acetate by the commercial preparation of horse serum cholinesterase was observed on a stopped-flow spectrophotometer. It was found that the transient process is a reaction of the ester with a major component of the preparation and is not caused by the serum cholinesterase enzyme. This noncholinesterase component was isolated and the dependence of its concentration and that of the ester upon the transient liberation of the indophenolate ion were determined. Studies with the isolated component and subsequent analyses have led to the tentative id...
Collins ND, LeRoy BE, Vap L.Extremely high bicarbonate (HCO3-) and anion gap values were measured in two horses and a calf using the Hitachi 911 automated serum biochemistry analyzer. All three animals had severe muscle disease as evidenced by markedly increased aspartate aminotransferase and creatine kinase activities. Laboratory error was suspected as the source of the increased HCO3- because values calculated from blood gas analysis were normal. It was hypothesized that increased serum lactate dehydrogenase (LDH) activity and pyruvate concentration overwhelmed the oxamate LDH inhibitor in the enzymatic HCO3- assay, re...
Gu XL, Dai FY, Xiao X, Li GZ, Zhang LM, Qu WJ.The effect of Ageratina adenophora on pathological characteristics of the liver and lungs as well as serum biochemical parameters in horses were investigated. Ten horses without ingestion history of Ageratina adenophora were classified into the control group, and 10 poisoned but survived horses with 3 months ingestion history were set as the case group. Results showed that serum AST, ALT, ALP, magnesium and phosphorus were elevated significantly, while creatinine was decreased remarkably. Hematoxylin and eosin staining of liver tissues showed diffuse swelling or destruction of hepatocytes, nar...
Monkos K.This paper presents the results of viscosity determinations on aqueous solutions of equine, porcine and rabbit serum albumin over a wide range of concentrations and at temperatures ranging from 5 degrees C to (42-45) degrees C. The results are compared with human and bovine serum albumin previously studied. Viscosity-temperature dependence is discussed on the basis of the modified Arrhenius formula. The effective specific volume, the activation energy and entropy of viscous flow for all investigated albumins are compared. Viscosity-concentration dependence, in turn, is discussed on the basis o...
Novelli EL, Rodrigues NL, Chiacchio SB.Biochemical values are widely related with environmental agents, sex and age, and are used in disease diagnosis. Numerous reports have been published on the biochemical parameters of different breeds of horses. However, there is a paucity of information concerning Cu-Zn superoxide dismutase (SOD), ceruloplasmin, copper and zinc determinations in the serum. Blood samples from a total of 60 horses of the Mangalarga-Paulista breed, representing three age groups (0 to 4 months old, 6 to 18 months old and adult) were examined. Male horses have a higher mean value of SOD, ceruloplasmin and copper th...
Brems DN, Liu YC, Stellwagen E.The heme iron of horse heart cytochrome c was selectively removed using anhydrous HF. The product, porphyrin c, exhibits the viscosity, far ultraviolet circular dichroic, and fluorescence properties characteristic for native cytochrome c. However, porphyrin c is more susceptible to denaturation by guanidine hydrochloride and by heat than is the parent cytochrome. All of the conformational parameters of porphyrin c exhibit a common reversible transition centered at 0.95 m guanidine hydrochloride at 23 degrees C and pH 7.0. Guanidine denatured porphyrin c refolds in two kinetic phases having tim...
Söylemez Z, Ozer I.The inhibition of horse plasma cholinesterase by propranolol showed characteristics which depended upon the identity of the substrate used. With butyrylthiocholine as substrate, the inhibition showed a first-order dependence on inhibitor concentration, and was characterized by a Ki of 8 microM (pH 7.4, 20 degrees C). With p-nitrophenylbutyrate as substrate, a biphasic v-1 versus [I] relationship was obtained. The biphasic curve could be resolved into two components, with apparent Ki's of 9 microM and 1.3 mM. Use of butyrylthiocholine as alternative substrate resulted in partial inhibition of p...
Hayami A, Darwish WS, Ikenaka Y, Nakayama SM, Ishizuka M.There is little information about drug metabolism and pharmacokinetics in horses. Therefore, it is necessary to characterize the profiles of drug metabolites for the safe use of drugs. In this study, we focused on cytochrome P450 enzymes (CYPs), which represent an important enzyme group to determine pharmacological effects of drugs. We chose diazepam as the drug of choice for this study. The aim of this study was to elucidate the metabolic pathway of diazepam in horses in comparison with rats, and to clarify CYP subfamilies responsible for diazepam metabolism in horses. Our results showed tema...
Duckworth DH, Madison JB, Calderwood-Mays M, Souba WW.Glutamine has been shown to be an important metabolic substrate of enterocytes in many animals, including cats, dogs, hamsters, human beings, monkeys, rabbits, rats, and sheep. To determine whether glutamine is important in the metabolism of cells of the equine gastrointestinal tract, we examined transintestinal differences in glutamine concentrations in the arterial and venous circulation, and measured activity of the major glutamine catabolizing enzyme, glutaminase. Arteriovenous differences provide an index of the amount of a given substrate removed by the tissue across which the measuremen...
Bardell DA, Archer DC, Milner PI.Colic remains a life-threatening condition in the horse. Ischaemia and reperfusion following correction of small intestinal strangulation may produce oxidative stress. The ability to withstand oxidative stress depends on antioxidant levels and may be linked to horse survival. Objective: To measure peripheral antioxidant levels in horses undergoing exploratory laparotomy with small intestinal strangulation. Methods: Case-control study. Methods: Blood and plasma were collected from horses undergoing exploratory laparotomy for small intestinal strangulation and stored at -80°C. Controls involved...
Szwarocka-Priebe T, Gill J.Twenty Thoroughbred 3 year old horses (10 stallions and 10 mares), trained and raced at the Warsaw Race-Course were studied from March through November. Blood was taken approximately every 8 weeks to determine the activities of aspartate and alanine transaminases, acid and alkaline phosphatases and aldolase. It was observed that the activities of aspartate aminotransferase and alkaline phosphatase reached their maxima in July and alanine transaminase in May. The activities of acid phosphatase and aldolase showed their minima in July. Comparing these data with the literature it was noted that t...
Kizaki T, Mizuno Y, Takasawa T, Shiokawa H.Analysis of the quantitative precipitin reaction of acylphosphatase from porcine skeletal muscle with rabbit antiserum indicated the presence of at least two antigenic determinants on the porcine enzyme molecule. Immunological cross-reactivities of acylphosphatases from equine and rabbit skeletal muscles were examined. In double immunodiffusion with the antiserum, the precipitin lines of the porcine and equine enzymes completely fused, while the rabbit enzyme gave no precipitin line. The reaction between the 125I-labeled porcine enzyme and its antibody was inhibited to the same extent by the p...
