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PubMed1981

Selective inactivation of lactate dehydrogenase isoenzymes with ionic surfactants.

Ionic surfactants selectively inactivate porcine lactate dehydrogenase (LDH) isoenzymes in 30 mM phosphate buffer, pH 7.4. The cationic surfactants hexadecylpyridinium bromide and hexadecyltrimethylammonium bromide rapidly inactivate LDH isoenzymes containing the B subunit; inactivation of LDH-A4 is slower and also retarded by the cofactor reduced nicotinamide adenine dinucleotide. The anionic surfactants sodium decyl sulfate and sodium dodecyl sulfate rapidly inactivate LDH isoenzymes containing the A subunit; inactivation of LDH-B4 is much slower and retarded by the cofactor. The selectivity of the inactivation process correlates with electrostatic interactions: positively charged surfactants preferentially inactivate isoenzymes containing a subunit of net negative charge, and negatively charged surfactants preferentially inactivate isoenzymes containing a subunit of net positive charge. Inactivation takes place near the critical micelle concentration for the cationic surfactants. Inactivation with anionic surfactants occurs above the critical micelle concentration. The cationic surfactants show little discrimination among LDH-B4 and the hybrid isoenzymes, AB3, A2B2, and A3B, inactivating all at approximately the same surfactant concentration. The anionic surfactants, however, show a more graded inactivation-concentration profile with discrete differences in threshold surfactant concentrations required for complete inactivation of the four A subunit containing isoenzymes. At a particular surfactant concentration, loss in activity can be correlated with the percent A- or B-subunit composition of the isoenzyme.

Animals↗
PubMed1972

The isocitrate dehydrogenases of Acinetobacter lwoffi. Separation and properties of two nicotinamide-adenine dinucleotide phosphate-linked isoenzymes.

Two isoenzymes of NADP-linked isocitrate dehydrogenase have been identified in Acinetobacter lwoffi and have been termed isoenzyme-I and isoenzyme-II. The isoenzymes may be separated by ion-exchange chromatography on DEAE-cellulose, by gel filtration on Sephadex G-200, or by zonal ultracentrifugation in a sucrose gradient. Low concentrations of glyoxylate or pyruvate effect considerable stimulation of the activity of isoenzyme-II. The isoenzymes also differ in pH-dependence of activity, kinetic parameters, stability to heat or urea and molecular size. Whereas isoenzyme-I resembles the NADP-linked isocitrate dehydrogenases from other organisms in having a molecular weight under 100000, isoenzyme-II is a much larger enzyme (molecular weight around 300000) resembling the NAD-linked isocitrate dehydrogenases of higher organisms.

Alcaligenes↗
PubMed1983

Alterations in phosphofructokinase isoenzymes during early human development. Establishment of adult organ-specific patterns.

Human 6-phosphofructokinase (EC 2.7.1.11) exists in tetrameric isoenzymic forms composed of muscle (M), liver (L) and platelet (P) subunits, which are under separate genetic control. In the adult, the proportion of these subunits in different organs reflects the relative activity of glycolysis versus gluconeogenesis. To elucidate the developmental basis for the observed distribution, we investigated the isoenzymic transitions of phosphofructokinase in human foetuses (12-40 weeks' gestation) by using high-resolution chromatography and monoclonal antibodies. We studied skeletal muscle, heart, liver and brain because these organs show very different glycolytic fluxes and isoenzymic patterns in adult individuals. Our results demonstrate that there is no unique 'foetal' form of phosphofructokinase in humans, but all three loci are variably expressed in all foetal organs during early gestation. As development proceeds, muscle and liver isoenzyme patterns show dramatic changes, with disappearance of P and L subunits in muscle and transient reappearance of M and P subunits in liver; in contrast, phosphofructokinase isoenzymes change little in brain and heart. Most changes occur at mid-gestation and near term, and adult isoenzyme patterns are expressed at birth, indicating that organ differentiation is complete. These studies show that phosphofructokinase undergoes changes of isoenzyme patterns similar to, but not identical with, those of other multilocus isoenzyme systems of glycolysis. The observed changes probably reflect changing patterns of gene expression, with repression of some loci and activation of others.

Brain↗
PubMed1985

Isoenzymes of phosphofructokinase in the rat. Demonstration of the three non-identical subunits by biochemical, immunochemical and kinetic studies.

In man and the rabbit, 6-phosphofructokinase (PFK, EC 2.7.1.11) exists in tetrameric isoenzymic forms composed of muscle (M or A), liver (L or B) and platelet or brain (P or C) subunits, which are under separate genetic control. In contrast, the genetic control of the rat PFK has not yet been conclusively established; it is unclear whether the P-type or C-type subunit exists in this species. To resolve this question, we investigated the enzyme from the skeletal muscle, liver and brain of rats of Wag/Rij strain. Our studies demonstrate that the rat PFK is also under the control of three structural loci and that the homotetramers M4, P4 and L4 exhibit unique chromatographic, immunological and kinetic-regulatory properties. Skeletal-muscle and brain PFKs consist of isolated M4 and P4 homotetramers respectively. Although liver PFK consists predominantly of L4 homotetramer, it also contains small amounts of PL3 and P2L2 species. All three PFKs exhibit allosteric properties: co-operativity with fructose 6-phosphate and inhibition by ATP decrease in the order P4 greater than L4 greater than M4. P4 and M4 tetramers are the most sensitive to citrate inhibition, whereas L4 tetramer is the least sensitive. More importantly, P4 and L4 isoenzymes are the most sensitive to activation by fructose 2,6-bisphosphate, whereas M4 isoenzyme is the least sensitive. These results indicate that the brain PFK in this strain of rat is a unique tetramer, P4, which also exhibits allosteric kinetics, as do the well-studied M4 and L4 isoenzymes. The reported differences in the number and nature of isoenzymes present in the rat brain and liver most probably reflect the differences in the strains studied by previous investigators. Since the nature of the rat PFK isoenzymes and nomenclatures reported by previous investigators have been now reconciled, it is proposed that, for the sake of uniformity, only well-established nomenclatures used for the rabbit or human PFK isoenzymes be used for the rat isoenzymes.

Adenosine Triphosphate↗
PubMed1988

Analysis of the phosphofructokinase subunits and isoenzymes in human tissues.

The 6-phosphofructo-1-kinase (PFK) subunits and isoenzymes were studied in human muscle, heart, brain, liver, platelets, fibroblasts, erythrocytes, placenta and umbilical cord. In each tissue, the subunit types in the native isoenzymes were characterized by immunological titration with subunit-specific antibodies and by column chromatography on QAE (quaternary aminoethyl)-Sephadex. Further, the subunits of the partially purified native isoenzymes were resolved by SDS/polyacrylamide-gel electrophoresis, identified by immunoblotting, and quantified by scanning gel densitometry of silver-stained gels and immunoblots. Depending on the type of tissue, one to three subunits were detected. The Mr values of the L, M and C subunits regardless of tissue were 76,700 +/- 1400, 82,500 +/- 1640 and 86,500 +/- 1620. Of the tissues studied, only the muscle PFK isoenzymes exhibited one subunit, which was the M-type subunit. Of the other tissues studied, the PFK isoenzymes contained various amounts of all three subunits. Considering the properties of the native PFK isoenzymes, it is clear that, in human tissues, they are not simply various combinations of two or three homotetrameric isoenzymes, but complex mixtures of homotetramers and heterotetramers. The kinetic/regulatory properties of the various isoenzyme pools were found to be dependent on subunit composition.

Adenosine Triphosphate↗
PubMed1993

Activation of purified human protein kinase C alpha and beta I isoenzymes in vitro by Ca2+, phosphatidylinositol and phosphatidylinositol 4,5-bisphosphate.

The increasing number of eukaryotic protein kinase C (PKC) isoenzymes which have been described has raised great interest in potential differences in the cellular expression, the mode of activation and the substrate specificity of these isoenzymes. The last two aspects have mostly been studied with isoenzymes purified from rat or bovine brain or from recombinant-baculovirus-infected insect cells. In this study, we have expressed the human PKC isoenzymes alpha and beta I in recombinant-baculovirus-infected insect cells. The isoenzymes were purified to homogeneity by a four-step procedure which included a reversible Ca(2+)-dependent association/dissociation to and from the endogenous membranes of the lysed insect cells. Characterization of the purified enzymes with respect to ATP requirement and substrate specificity, using the epidermal-growth-factor receptor peptide and histone III-S respectively, revealed no isoenzyme-specific differences. Activation by trypsin or Ca2+ and a variety of different phospholipids and phosphoinositides (in a mixed-micellar assay) gave the following results. Proteolytic cleavage of the PKC isoenzymes by trypsin generated fully activated phospholipid-independent PKC beta I, whereas PKC alpha reached only 50% of the activity obtained in the presence of phospholipids. PKC alpha and beta I showed no difference in their dependence on Ca2+, diacylglycerol (DAG) and phosphatidylserine (PS). Replacement of either DAG or PS by phosphatidylglycerol, cardiolipin, phosphatidylcholine and several phosphoinositides revealed that PtdIns(4,5)P2 can act as a PKC activator similar to DAG, whereas PtdIns can substitute for PS as a cofactor of activation. Thus, at least for the PKC isoenzymes alpha and beta I, a combination of PtdIns and PtdIns(4,5)P2 can fully replace PS and DAG in vitro as the classical activators of PKC.

Adenosine Triphosphate↗
PubMed1989

Monoclonal antibodies against rat glutathione S-transferase isoenzymes 2-2 and 3-3.

Monoclonal antibodies were prepared against rat glutathione S-transferase isoenzymes 2-2 and 3-3. Three clones were capable of specifically differentiating their respective antigens from other rat isoenzymes as well as human isoenzymes, in ELISA and on Western blot. One clone produced antibodies specific for isoenzyme 2-2, and 2 hybridomas were specific for isoenzyme 3-3. Balb/c mice did not respond to immunization with glutathione S-transferase isoenzymes 1-1 and 4-4. However, an immune response was obtained in some other strains of mice, with differential H-2 haplotypes, notably CBA/BrARij mice and CBA/CaHRij-T6 mice for isoenzyme 1-1 and CBA/BrARij mice for isoenzyme 4-4, which offers perspectives for obtaining additional specific monoclonal antibodies against these glutathione S-transferases.

Animals↗
PubMed1977

Subcellular compartmentation of creatine kinase isoenzymes in guinea pig heart.

In an attempt to determine whether a subcellular compartmentation of creatine kinase exists and if so, whether there is a different distribution of the 3 isoenzymes of CK in the cell, studies were carried out with the guinea pig heart which had been subfractionated by either isopycnic density gradient centrifugation or differential pelleting. Isoenzyme analysis of CK in the isolated subcellular fractions by electrophoresis on agarose gels, revealed that the MM isoenzyme occurred in the cytosol, myofibrils, and the microsomes while the MB isoenzyme (which is cardio-specific) was only found in the cytosol. Trace amounts of the BB isoenzyme were detected in the cytosol. Considerable CK activity was associated with the mitochondria, this did not represent the MM, the MB, or the BB isoenzymes but was a distinct and additional mitochondrial-specific form of CK. PH optima and kinetic studies were carried out to characterise and distinguish the mitochondrial isoenzyme from other CK isoenzyme activity. The evidence for a differential compartmentation of MM, MB, BB, and mitochondrial CK is discussed in relation to their possible cellular roles.

Animals↗
PubMed2002

5alpha-reductase isoenzymes 1 and 2 in the rat testis during postnatal development.

The pubertal initiation of spermatogenesis is reliant on androgens, and during this time, 5alpha-reduced androgens such as dihydrotestosterone (DHT) are the predominant androgens in the testis. Two 5alpha-reductase (5alphaR) isoenzymes (5alphaR1 and 5alphaR2) have been identified, which catalyze the conversion of testosterone to the more potent androgen DHT. The present study aimed to investigate the developmental pattern of 5alphaR isoenzymes and their relationship to the production of 5alpha-reduced androgens in the postnatal rat testis. Both 5alphaR1 and 5alphaR2 isoenzyme mRNAs were measured by real-time polymerase chain reaction, isoenzyme activity levels by specific assays, and testicular androgens by radioimmunoassay after high-performance liquid chromatographic separation. Both 5alphaR1 and 5alphaR2 mRNAs and activity levels were low in the 10-day-old (prepubertal) testis, peaked between Days 20 and 40 during puberty, and then declined to low levels at 60-160 days of age. The developmental pattern of both 5alphaR isoenzyme activity levels was mirrored by the testicular production of 5alpha-reduced metabolites. Although 5alphaR1 was greater than 5alphaR2 at all ages, it is likely, given the substrate preferences of the two, that both isoenzymes contribute to the pubertal peak of 5alpha-reduced androgen biosynthesis. The peak in 5alphaR isoenzymes and 5alpha-reduced metabolite production coincided with the first wave of spermatogenesis in the rat, suggesting a role for 5alpha-reduced metabolites in the initiation of spermatogenesis. This was explored by acute administration of a 5alphaR inhibitor (L685,273) to immature rats. The L685,273 markedly suppressed testicular 5alphaR activity during puberty by 75%-86%. However, a marked increase was observed in testicular testosterone levels (in the absence of changes in LH), and no decrease was observed in the absolute levels of 5alpha-reduced metabolites. Therefore, whether the formation of DHT in the presence of low testosterone levels in the pubertal testis is required for the initiation of spermatogenesis cannot be tested using 5alphaR inhibitors. We conclude that both 5alphaR1 and 5alphaR2 isoenzymes are involved in the peak of 5alpha-reduced androgen biosynthesis in the testis during the pubertal initiation of spermatogenesis.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1997

Changes in serum creatine phosphokinase MM isoenzyme after lumbar spine surgery.

STUDY DESIGN: Serum concentrations of creatine phosphokinase and its isoenzyme were measured serially in 47 patients who underwent lumbar surgery. OBJECTIVE: To analyze the significance of postoperative creatine phosphokinase MM levels as indicators of muscle trauma after lumbar surgery. SUMMARY OF BACKGROUND DATA: The authors of the present study previously have reported on iatrogenic back muscle injury in an animal model and in man. However, the relationship between the change of the creatine phosphokinase MM isoenzyme level and muscle injury after surgery has not been clarified. METHODS: Peripheral venous blood samples were collected serially before surgery, just after surgery, and at 1, 3, 7, 14, and 21 days after surgery. The serum concentration of total creatine phosphokinase and its isoenzymes was measured by agarose gel electrophoresis. The serial postoperative change of the creatine phosphokinase MM isoenzyme concentration was evaluated with respect to age, gender, body weight, types and levels of surgery, and surgery time. RESULTS: Creatine phosphokinase MM activity increased after surgery and reached a maximum value 1 day after surgery, followed by recovery to the normal value 1 week after surgery. The maximum concentration of creatine phosphokinase MM isoenzyme in posterior lumbar surgery was significantly higher than that in anterior surgery (P = 0.04). It was significantly higher in men than in women (P = 0.02). Serum concentration of creatine phosphokinase MM isoenzyme showed no significant correlation to the extent of muscle exposure and surgery time. CONCLUSION: The time course of postoperative serum creatine phosphokinase MM isoenzyme activity is correlated with the histologic changes of the back muscles after surgery. The concentration of creatine phosphokinase MM isoenzyme in posterior lumbar surgery was significantly higher than that in anterior surgery. It was also significantly higher in men than in women.

Adolescent↗
PubMedDate not supplied

Kinetic characterization of two classes of dog liver alcohol dehydrogenase isoenzymes.

In order to relate the catalytic properties of alcohol dehydrogenase (ADH), the rate-limiting enzyme for alcohol metabolism, with the pharmacokinetics of ethanol elimination in vivo, the multiple molecular forms of dog liver ADH were purified and their steady state kinetics investigated. Two different classes of ADH forms were identified by starch gel electrophoresis: the class I isoenzymes migrate to the cathode and the class II forms migrate to the anode. Three different patterns of the cathodic class I isoenzymes were identified in different liver specimens. Three molecular forms were observed for patterns A and C, and five for B. The two classes of isoenzymes were separated by affinity chromatography and purified by column chromatography. The three predominant class I isoenzymes, A1, B2, and C1, in type A, B, and C livers, respectively, were isolated by high performance cation-exchange chromatography. The steady state kinetic constants of the A1, B2, and C1 isoenzymes are similar, but differ substantially from those of the class II enzyme. The class II enzyme is much less sensitive to pyrazole inhibition, Ki = 2 mM, than the class I forms, Ki = 0.6 microM. Methanol is not a substrate for the class II enzyme, whereas it is oxidized by the class I isoenzymes. The class I isoenzymes exhibit a lower Km and substrate inhibition Ki for ethanol, 0.4 and 160 mM, respectively, than values for the class II enzyme, 10 and 610 mM, respectively. The properties of class I and II dog liver ADH are similar to those of the respective isoenzymes purified from human and monkey liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Oxidoreductases↗
PubMed1989

Urinary lactic dehydrogenase isoenzyme analysis in children with spinal lesions.

In 48 children with spinal lesions and micturition problems urinary lactic dehydrogenase (LDH) isoenzymes were analyzed. They had higher total LDH activities (716.8 +/- 1,050.2 nkat/I), isoenzymes V percents (22.2 +/- 13.0%) and isoenzyme V activities (203.4 +/- 308.4 nkat/I) than those of healthy children (150.0 +/- 83.4 nkat/I, 1.9 +/- 1.0%, 5.0 +/- 3.3 nkat/I). Many subjects had an isoenzyme V-dominant LDH isoenzyme pattern. Among 48 subjects the patients with pyuria, bacteriuria or abnormal pyelograms had markedly high total LDH activities, isoenzyme V percents and isoenzyme V activities. The rise in LDH isoenzyme V levels may reflect the renal damage in the patients with neurogenic bladders.

Adolescent↗
PubMed1989

Isoenzyme analysis of typhoid-Shigella and Escherichia-Shigella hybrid vaccines and their parental strains.

Isoenzyme analysis can be used to measure phenotypic changes and to characterize bacterial strains. The use of isoenzyme analysis to characterize bacterial hybrid vaccine strains that were prepared for human vaccination is described in this report. The hybrid vaccine strains were two lots of Salmonella typhi-Shigella sonnei vaccine, two lots of Escherichia coli-Shigella flexneri vaccine, and their parental strains. The two lots of S. typhi-S. sonnei hybrid vaccine had only 5 of 11 reactive isoenzymes in common. The lot of S. typhi-S. sonnei hybrid vaccine that protected human volunteers in a clinical trial also had a greater degree of relatedness to the parental strain, S. typhi Ty21a, than the nonprotective lot. The two lots of E. coli-S. flexneri vaccine were more similar in terms of their isoenzyme profiles. There were colonial isolates from both lots that had identical isoenzyme profiles. The results also indicate a greater degree of homogenicity between Shigella spp. and E. coli than between either of these species and Salmonella spp. The data also show more isoenzyme activity associated with the nonpathogenic bacteria than with pathogenic isolates. Isoenzyme analysis is a rapid and specific assay that can be used to evaluate bacterial vaccine organisms and to establish isoenzyme profiles associated with vaccine immunogenicity and efficacy.

Bacterial Vaccines↗
PubMed1980

Fetal isoenzyme expression of heterotransplanted HeLa cells in nude mice.

The nude mouse has been successfully employed for the propagation of human tumors, without the need for immunosuppression. In light of the limited data on embryonic gene expression in such tumors, we undertook a study of fetal isoenzyme expression during tumor growth. HeLa TCRC-1 which has been shown to produce the placental Regan isoenzyme was used in these studies. The isoenzyme produced by these cells in culture is initially replaced by an isoenzyme referred to as chorionic. In the later stages of tumor growth, the so-called oncoamniotic (FL) isoenzyme then becomes the dominant enzyme form. The chorionic isoenzyme is produced by the early chorionic membranes of the developing conceptus, while the oncoamniotic (FL) isoenzyme is most similar to that found in the fetal human intestine. The alteration in the expression of fetal isoenzymes in tumors growing in the nude mouse is similar to that seen in the immunosuppressed rat and hamster host animals, indicating that the phenomenon is not related to immunosuppression per se.

Alkaline Phosphatase↗
PubMed1980

Clinical usefulness of the simultaneous localisation of the isoenzymes of alkaline phosphate and gamma-glutamyl transferase.

Simultaneous localisation of the isoenzymes of alkaline phosphatase and gamma-glutamyl transferase was carried out on 173 serum samples from patients with hepatobiliary and bone disease to determine (i) if a better discrimination of the underlying pathology could be obtained by such an approach, and (ii) if the pathology suggested by the alkaline phosphatase isoenzyme separation could help in determining the cellular location of the gamma-glutamyl transferase isoenzymes. It was found that the localisation of the gamma-glutamyl transferase isoenzymes had, with a few exceptions, little advantage over the measurement of the total activity but that some evidence concerning the cellular location of the gamma-glutamyl transferase isoenzymes could be gained by such an approach. There was support for the view that the alpha 2-migrating isoenzyme is derived from the liver parenchymal cytoplasm, but little support for the view that the alpha 1-migrating isoenzyme is predominantly the induced microsomal enzyme or that the beta-migrating isoenzyme is the result of impaired biliary secretion.

Alkaline Phosphatase↗
PubMed1984

Fructose feeding increases Ca++-activated myosin ATPase activity and changes myosin isoenzyme distribution in the diabetic rat heart.

Previous studies have shown that in rats, diabetes mellitus induces a 45% decrease in cardiac Ca++-activated myosin ATPase activity which is accompanied by a decrease in myosin isoenzyme V1 and an increase in myosin isoenzyme V3 levels. Insulin administration reverts Ca++-activated myosin ATPase activity and myosin isoenzyme distribution to normal levels. It is currently unclear whether the effects of insulin on Ca++-myosin ATPase activity and myosin isoenzyme distribution are direct effects of the hormone or are mediated through insulin-induced alterations in cardiac metabolism. To determine if insulin may exert part of its effects by the latter route, diabetic rats were fed a normal, glucose, or fructose diet. Unlike glucose, fructose can enter the initial steps of the glycolytic pathway in the absence of insulin. Placing diabetic rats on different forms of 60% fructose diets for 4 weeks led to a 20-35% increase in Ca++-activated myosin ATPase activity, which was highly significant (normal Ca++-activated myosin ATPase activity, 0.917 mumol Pi/mg protein X min; diabetic, 0.553 mumol Pi/mg protein X min; diabetic + fructose, 0.661 mumol Pi/mg protein X min). The increase in Ca++-activated myosin ATPase activity was accompanied by increased myosin isoenzyme V1 and decreased myosin isoenzyme V3 levels. Feeding animals a 60% glucose diet did not lead to changes in Ca++-activated myosin ATPase activity or myosin isoenzyme distribution. The fructose-induced increase in Ca++-activated myosin ATPase activity and alteration in myosin isoenzyme distribution occurred in the absence of changes in insulin and thyroid hormone levels or improvement in the general metabolic status of fructose-fed diabetic rats.

Adenosine Triphosphatases↗
PubMed1994

Significance of adenosine deaminase activity and its isoenzymes in tuberculous effusions.

Adenosine deaminase (ADA) activity is increased in effusions caused by certain clinical conditions including tuberculosis and bacterial infections. In this study, the ADA isoenzyme patterns in tuberculous and parainfective effusions were investigated to determine the isoenzyme responsible for this increase in activity. Fifty-one tuberculous effusions and six parainfective effusions were investigated. All effusions had increased ADA activity (median values of 126 and 127 units/L, respectively). In the tuberculous effusions, ADA2 isoenzyme was found to be primarily responsible for total activity, with a median contribution of 88 percent. The ADA1 (both ADA1m and ADA1c isoenzymes) was the major isoenzyme in the parainfective effusions with a median contribution of 70 percent. The ADA2 isoenzyme activity most likely reflects monocyte-macrophage turnover or activity, while ADA1 probably originates from lymphocytes or neutrophils. It is therefore essential to determine the isoenzyme profile when interpreting ADA activity levels in effusions. The measurement of the individual isoenzymes will enhance the diagnostic utility of ADA activity determinations in pleural effusions.

Adenosine Deaminase↗
PubMed1995

Biochemical and enzymological study of lactate dehydrogenase isoenzymes from commercial quality control sera and several animal tissue sources.

We assayed the isoenzymes of lactate dehydrogenase (EC 1.1.1.27) in commercial quality control sea and several animal tissue extracts, using electrophoresis. We compared the Km values and activation energies of the isoenzymes, in order to find suitable animal tissue sources with a similar isoenzyme profile to that of human serum lactate dehydrogenase. Some of the control sera contained only one isoenzyme fraction corresponding to porcine heart isoenzyme-1 or chicken heart isoenzyme-1, which showed essentially no changes of enzyme activity as a function of pyruvate substrate concentration. Other control sera, which contained isoenzymes from human red cells haemolysates, or from animal tissue extracts with a human serum matrix, showed significant changes of enzyme activity was a function of substrate concentration, and showed different Km values and activation energies from those of human serum. Of the serum and tissue samples from several animal sources, rat heart and kidney extracts showed the greatest similarity to human serum, with respect to the electrophoretic pattern and the Km, pH optimum and activation energy of lactate dehydrogenase isoenzymes.

Animals↗