24R,25-dihydroxyvitamin D stimulates creatine kinase BB activity in chick cartilage cells in culture

In chick limb-bud cartilage cell cultures 24R,25-dihydroxycholecalciferol (24R,25(OH)2D3), but not 24S,25(OH)2D3, 1 alpha,25(OH)2D3 or 25(OH)D3, stimulates the activity of the brain type (BB) isozyme of creatine kinase (EC 2.7.3.2), the 'estrogen-induced protein' first identified in rat uterus. Cultures treated with bromodeoxyuridine, in which cartilage formation is inhibited, show no stimulation of creatine kinase BB by 24R,25(OH)2D3.     

DT56a (Tofupill/Femarelle) selectively stimulates creatine kinase specific activity in skeletal tissues of rats but not in the uterus

The novel natural product DT56a (Tofupill/Femarelle), derived from soybean, has been shown to relieve menopausal vasomotor symptoms and to increase bone mineral density with no effect on sex steroid hormone levels or endometrial thickness. In the present study, we compared the effects of DT56a and estradiol-17beta (E2) on bone and cartilage (Ep) of immature or ovariectomized female rats, by measuring the changes in the specific activity of the BB isozyme of creatine kinase (CK). Single short-term injection of high doses of DT56a induced estrogenic activity in bones and uterus similar to that of E2. When administered in multiple oral doses, DT56a stimulated skeletal tissues similarly to E2, but whereas E2 increased CK specific activity in the uterus, DT56a did not. The selective estrogen receptor modulator (SERM) raloxifene (Ral) blocked the stimulation of CK by either DT56a or by E2 in all tissues tested. Our findings suggest that DT56a acts as a selective estrogen receptor modulator stimulating skeletal tissues without affecting the uterus. The effect of DT56a on other systems, such as the vascular and the central nervous system, are currently under investigation.     

Is the subunit the minimal function unit of creatine kinase?

The dimeric rabbit muscle isozyme of creatine kinase (MM) is modified by iodoacetamide to produce the inactive dimer (M'M') and then hybridized with native dimeric brain isozyme (BB). The hybrid enzyme (M'B), as isolated by PAGE, has the same Km for both ATP and creatine but half the specific activity of the brain isozyme (BB). Likewise, the hybrid of the modified brain with the native muscle isozyme (MB') has half the activity of the native muscle enzyme. The M'B, MB' and MB hybrid dimers all have essentially the same electrophoretic properties, and their intrinsic fluorescence and CD spectra in the far-ultraviolet region are very similar to those of the homodimers MM and BB. Similar results were obtained for the hybrid (M"B) containing the muscle enzyme subunit modified at both the thiol group with iodoacetamide and the Trp residue with dimethyl(2-hydroxy-5-nitrobenzyl)sulfonium bromide and the native brain enzyme submit. The above results suggest strongly the independent catalytic function of the subunit of creatine kinase.     

Rate equation for creatine kinase predicts the in vivo reaction velocity: 31P NMR surface coil studies in brain, heart, and skeletal muscle of the living rat

Brain, heart, and skeletal muscle contain four different creatine kinase isozymes and various concentrations of substrates for the creatine kinase reaction. To identify if the velocity of the creatine kinase reaction under cellular conditions is regulated by enzyme activity and substrate concentrations as predicted by the rate equation, we used 31P NMR and spectrophotometric techniques to measure reaction velocity, enzyme content, isozyme distribution, and concentrations of substrates in brain, heart, and skeletal muscle of living rat under basal or resting conditions. The total tissue activity of creatine kinase in the direction of MgATP synthesis provided an estimate for Vmax (23.4 +/- 2.8, 62.4 +/- 4.5, and 224 +/- 16 mM/s) and exceeded the NMR-determined in vivo reaction velocities by an order of magnitude (4.1 +/- 1.2, 5.1 +/- 1.6, and 18.4 +/- 2.4 mM/s for brain, heart, and skeletal muscle, respectively). The isozyme composition varied among the three tissues: greater than 99% BB for brain; 14% MB, 61% MM, and 25% mitochondrial for heart; and 98% MM and 2% mitochondrial for skeletal muscle. The NMR-determined reaction velocities agreed with predicted values from the creatine kinase rate equation (r2 = 0.98; p less than 0.001). The concentrations of free creatine and cytosolic MgADP, being less than or equal to the dissociation constants for each isozyme, were dominant terms in the creatine kinase rate equation for predicting the in vivo reaction velocity. Thus, we observed that the velocity of the creatine kinase reaction is regulated by total tissue enzyme activity and by the concentrations of creatine and MgADP in a manner that is independent of isozyme distribution.     

Tissue selective action of tamoxifen methiodide, raloxifene and tamoxifen on creatine kinase B activity in vitro and in vivo

We have compared the cell and tissue selective estrogenic and antiestrogenic activities of tamoxifen, raloxifene, ICI 164,384 and a permanently ionized derivative of tamoxifen — tamoxifen methiodide (TMI). This non-steroidal antiestrogen has limited ability to cross the blood brain barrier and is therefore less likely to cause the central nervous system disturbances caused by tamoxifen. We have used the stimulation of the specific activity of the “estrogen induced protein”, creatine kinase BB, as a response marker in bone, cartilage, uterine and adipose cells and in rat skeletal tissues, uterus and mesometrial adipose tissue. In vitro, TMI, tamoxifen and raloxifene mimicked the agonistic action of 17β-estradiol in ROS 17/2.8 rat osteogenic osteosarcoma, female calvaria, and SaOS₂ human osteoblast cells. In Ishikawa endometrial cancer cells, tamoxifen showed reduced agonistic effects and raloxifene showed no stimulation. However, as antagonists, tamoxifen and raloxifene were equally effective in Ishikawa or SaOS₂ cells. In immature rats, all four of the antiestrogens inhibited estrogen action in diaphysis, epiphysis, uterus and mesometrial adipose tissue; when administered alone, tamoxifen stimulated creatine kinase (CK) specific activity in all these tissues. Raloxifene and TMI, however, stimulated only the skeletal tissues and had no stimulatory effect in the uterus or mesometrial fat, and the pure antiestrogen ICI 164,384 showed no stimulatory effect in any of the tissues. The simultaneous injection of estrogen, plus an antiestrogen which acted as an agonist, resulted in lower CK activity than after injection of either agent alone. These differential effects, in vivo and in vitro, may point the way to a wider therapeutic choice of an appropriate antiestrogen which, although antagonizing E₂ action in mammary cancer, can still protect against osteoporosis and cardiovascular disease and not stimulate the uterus with its attendant undesirable changes, or interfere with the beneficial action of E₂ in the brain.     

Characterization of a brain particulate bound form of creatine kinase

A bound form of creatine kinase associated with brain particulate was characterized by isoelectric focusing, antigenicity and chromatography and compared to muscle (MM), brain (BB), and heart mitochondrial isoenzymes. On partial purification and isoelectric focusing, the solubilized enzyme has a pl of 7.3, similar to the pl of muscle creatine kinase MM, pl 6.8, but different from brain creatine kinase BB, which precipitates on isoelectric focusing in sucrose or glycerol stabilized media at its calculated pl of 5.6. Gel filtration chromatography of deoxycholate solubilized particulate creatine kinase on Sephadex Gl50 reveals an estimated molecular weight of approximately 80,000 daltons. The brain particulate enzyme is antigenically distinct from both muscle and rat heart mitochondrial creatine kinase isoenzymes but has antigenic similarity with soluble cytoplasmic brain BB. The situation may be analogous to that found with rat heart mitochondria and rat heart cytoplasmic isoenzymes which we have shown to exhibit antigenic similarity even though differences in electrophoretic and amino acid composition have been demonstrated; however, the confident determination that the particulate enzyme is a separate isoenzyme will have to await amino acid analysis.     

Differences in the induction of thymidine kinase isozymes in estrogen-treated immature and adult rats

Thymidine kinase activity in immature and castrated adult rat uterus has been examined in respose to estrogen treatment. Following estrogen administration. it was found that immature uterine thymidine kinase activity was increased 30-fold after 24 h, but almost no effect was produced on castrated or non-castrated adult uterus. Uterine thymidine kinase activity was separated into three peaks (peak 1, 2 and 3) by means of DEAE-cellulose column chromatography. In response to estrogen, the thymidine kinase isozymes differed in adult and immature uteri. In immature uteri, marked and selective increase of the activity was found in peak I, whereas in adult only a slight increase in peak 2 activity was observed. The thymidine kinase activity in peak 1 and peak 2 were found to have different enzymatic properties and molecular weight, as determined by gel filtration of 125 000 for peak 1 and 100 000 for peak 2.From these results, it is suggested that estrogen induces specific thymidine kinase isozyme in immature uterus and that the isozyme may be involved in DNA synthesis. Such a induction mechanism seems to be lost during the development.     

Responsiveness of the 5′-flanking region of the brain type isozyme of creatine kinase to estrogens and antiestrogen

The brain type isozyme of creatine kinase (CKB) has proven to be a useful early marker for the action of steroid and other hormones. An increase in the steady state level of mRNA for CKB was found within 30 min after estrogen stimulation of immature rat uteri. Cycloheximide treatment did not inhibit CKD induction. In order to study the molecular mechanism of this induction, 2.9 kb of the 5′-flanking region of CKB fused with the CAT reporter gene was contransfected into ROS 17/2.8 and HeLa cells along with an expression plasmid for the human estrogen receptor. 17 β-Estradiol at 10⁻⁸ M or greater concentrations and the antiestrogen tamoxifen at 10⁻⁶ M stimulated CAT activity. When given simultaneously with 17 β-estradiol, tamoxifen showed a synergistic effect.     

Purification and characterization of creatine kinase isozymes from the nurse shark Ginglymostoma cirratum

Creatine kinase from nurse shark brain and muscle has been purified to apparent homogeneity. In contrast to creatine kinases from most other vertebrate species, the muscle isozyme and the brain isozyme from nurse shark migrate closely in electrophoresis and, unusually, the muscle isozyme is anodal to the brain isozyme. The isoelectric points are 5.3 and 6.2 for the muscle and brain isozymes, respectively. The purified brain preparation also contains a second active protein with pI 6.0. The amino acid content of the muscle isozyme is compared with other isozymes of creatine kinase using the Metzger Difference Index as an estimation of compositional relatedness. All comparisons show a high degree of compositional similarity including arginine kinase from lobster muscle. The muscle isozyme is marginally more resistant to temperature inactivation than the brain isozyme; the muscle protein does not exhibit unusual stability towards high concentrations of urea. Kinetic analysis of the muscle isozyme reveals Michaelis constants of 1.6 mM MgATP, 12 mM creatine, 1.2 mM MgADP and 50 mM creatine phosphate. Dissociation constants for the same substrate from the binary and ternary enzyme-substrate complex do not differ significantly, indicating limited cooperatively in substrate binding. Enzyme activity is inhibited by small planar anions, most severely by nitrate. Shark muscle creatine kinase hybridizes in vitro with rabbit muscle or monkey brain creatine kinase; shark brain isozyme hybridizes with monkey brain or rabbit brain creatine kinase. Shark muscle and shark brain isozymes, under a wide range of conditions, failed to produce a detectable hybrid.     

Creatine kinase isoenzymes in Torpedo californica: absence of the major brain isoenzyme from nicotinic acetylcholine receptor membranes

Creatine kinase, actin, and nu 1 are three proteins of Mr 43 000 associated with membranes from electric organ highly enriched in nicotinic acetylcholine receptor. High levels of creatine kinase are required to maintain adequate ATP levels, while actin may play a role in maintaining the synaptic cytoskeleton. Previous investigations have prompted the conclusion that postsynaptic specializations at the receptor-enriched membrane domains in electroplax contain the brain form of creatine kinase rather than the form of creatine kinase predominantly found in muscle. We have examined this conclusion by purifying Torpedo brain creatine kinase to virtual homogeneity in order to examine its immunochemical, molecular, and electrophoretic properties. On the basis of immunological cross-reactivity and isozyme analysis, the receptor-associated creatine kinase is identified to be of the muscle type. When the molecular characteristics of Torpedo brain and muscle creatine kinase are compared, the brain enzyme is positioned at a more basic pH during chromatofocusing and on two-dimensional gel electrophoresis (pI = 7.5-7.9). Furthermore, electrophoretic mobilities of the brain and muscle forms of creatine kinase differ in sodium dodecyl sulfate electrophoresis: the brain isozyme of creatine kinase has lower apparent molecular weight (Mr 41 000) when compared with the muscle enzyme (Mr 43 000). On the basis of the results of our current investigations, the hypothesis that the brain isozyme of creatine kinase is a component of the postsynaptic specializations of the Torpedo californica electroplax must be abandoned. Recent sequence data have established close homology between Torpedo and mammalian muscle creatine kinases. On the basis of electrophoretic criteria, our results indicate that a lower degree of homology exists between the brain isozymes.     

Parathyroid hormone induction of creatine kinase activity and DNA synthesis is mimicked by phospholipase C, diacylglycerol and phorbol ester

Parathyroid hormone (PTH), which increases cAMP levels, also induces an increase in the activity of the brain isozyme of creatine kinase and in DNA synthesis in osteoblast-enriched bone cell cultures by a cAMP-independent mechanism. The following results lead us to the conclusion that PTH induction of brain isozyme of creatine kinase activity and DNA synthesis occurs by activation of membranal phospholipid metabolism leading to increased protein kinase C activity and Ca2+ mobilization, a mechanism demonstrated for several growth factors and other hormones. (1) Binding of membranal phospholipids by agents such as gentamycin or antiphospholipid antibodies abolishes the stimulation by PTH of creatine kinase activity and DNA synthesis but not of cAMP production. (2) Treatment of cell cultures with exogenous phospholipase C increases brain isozyme of creatine kinase activity and DNA synthesis, but not cAMP production; these stimulations are also blocked by serum containing anti-phospholipid antibodies. PTH has no additional effect on stimulation of creatine kinase activity by phospholipase C (and only a slight effect on DNA synthesis). (3) A synthetic diacylglycerol (1-oleyl-2-acetyl glycerol) or phorbol ester (phorbol 12-myristate 13-acetate) or Ca2+ ionophore, A23187 induces creatine kinase activity and DNA synthesis in the cultures. However, this effect is not blocked by antiphospholipid sera and PTH has no additional effect. (4) Inhibition of protein kinase C activity by drugs reported to inhibit the enzyme (retinoic acid, quercetin) abolishes the stimulation of brain isozyme of creatine kinase activity and of DNA synthesis by PTH.     

Comparison between muscle and liver enolases and their behavior during differentiation and growth.

1. Rabbit liver enolase (EC 4.2.1.11) was purified about 200-fold and the enzyme was distinguished from crystalline muscle enolase by column isoelectrofocusing. It was found that the pI of muscle enolase was at about pH 8.8 and the pI of liver enolase was at about pH 6.7. Liver enolase was more liable to heat than muscle enolase. Anti-muscle enolase antibody did not react with liver enolase in double diffusion and immunoprecipitation tests. No substantial difference seemed to exist between muscle and liver enolases in pH optima, kinetic constants, and gel filtration. 2. It was observed by electrofocusing that the pI of rat muscle enolase was pH 7.2 to 7.9 and that of liver enolase was about pH 5.9. The main component of muscle enolase was designated as type A enolase, and liver enolase as type B enolase. Type A enolase was present in skeletal muscle and heart muscle. Type B enolase was widely distributed and present in liver, kidney, spleen, brain, lung, small intestine, and heart muscle. More acidic isozyme than type B enolase coexisted in the brain, and more basic isozyme than type A enolase, coexisted in the small intestine. A prototype of enolase in the early stage of differentiation was found to be type B enolase and, as differentiation progressed, type B decreased in muscle, while type A increased. On the other hand, liver enolase was retained as type B during differentiation. The enolase in regenerating liver was the same as in normal liver.     

Rat brain glycolysis regulation by estradiol-17 beta.

The effect of estradiol-17 beta on the activities of glycolytic enzymes from female rat brain was studied. The following enzymes were examined: hexokinase (HK, EC 2.7.1.1), phosphofructokinase (PFK, EC 2.7.1.11), aldolase (EC 4.1.2.13), glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12), phosphoglycerate kinase (EC 2.7.2.3), phosphoglycerate mutase (EC 2.7.5.3), enolase (EC 4.2.1.11) and pyruvate kinase (PK, EC 2.7.1.40). The activities of HK (soluble and membrane-bound), PFK and PK were increased after 4 h of hormone treatment, while the others remained constant. The changes in activity were not seen in the presence of actinomycin D. The significant rise of the activities of the key glycolytic enzymes was also observed in the cell culture of mouse neuroblastoma C1300 treated with hormone. Only three of the studied isozymes, namely, HKII, B4 and K4 were found to be estradiol-sensitive for HK, PFK and PK, respectively. The results obtained suggest that rat brain glycolysis regulation by estradiol is carried out in neurons due to definite isozymes induction.     

Detection of creatine kinase isoenzymes as tumoral markers of rhabdomyosarcoma.

We analyzed the expression profile of isoenzymatic fractions of creatine phosphokinase (EC 2.7.3.2) isotypes MM, MB and BB in three cell lines derived from embryonic rhabdomyosarcomas and a normal counterpart cell line. Electrophoretic data showed that the BB fraction was consistently expressed de novo, in contrast with its counterpart in normal tissue. The BB fraction may serve as new tumoral marker for the diagnosis of rhabdomyosarcoma. In addition, the appearance of macrocreatine kinase type-1 in this type of neoplasm may serve to reinforce the diagnosis when rhabdomyosarcoma is suspected.     

Isozymes of creatine kinase in mammalian cell culures

Previous studies on the energy metabolism of rat myocardial cells in culture supported the hypothesis that the creatine-phosphocreatine–creatine kinase system plays an important role in the intracellular transport of energy from the mitochondria to the myofibrils and in the regulation of energy production coupled to energy utilization in this model system. Effective functional compartmentation of ATP could result from the binding of creatine kinase to cellular organelles (e.g., myofibrils and mitochondria) such that high energy charge at the myofibrils is maintained by the reverse creatine kinase reaction, while phosphocreatine is synthesized mainly at the mitochondria in the forward creatine kinase reaction. It was, therefore, essential to demonstrate the presence of mitochondrial creatine kinase in the cultured myocardial cells to support this hypothesis, particularly since the mitochondrial creatine kinase was reportedly absent in fetal hearts. Using electrophoresis on cellulose acetate strips, the mitochondrial creatine kinase isozyme, as well as MM, MB, and BB isozymes, have now been demonstrated in myocardial cultures derived from neonatal rats. The mitochondrial creatine kinase increased with age in culture and with age of animal from which the culture is derived. Furthermore, the addition of creatine to culture media stimulates its synthesis. The mitochondrial creatine kinase isozyme was not detected in nonmuscle cells in culture derived from the neonatal rat hearts, nor in L6 muscle cell line. Phosphocreatine was present in all cells, but the regulation of energy metabolism and energy shuttle by creatine-phosphocreatine–creatine kinase could be operative only in the cells where the mitochondrial creatine kinase is present. This regulatory mechanism provides for an efficient system concomitant with the continuous energy demand of the myocardium; it is not ubiquitous and its development in myocardial cells seems to be triggered postnatally.     

Antigenic properties of BB creatine kinases from various tissues in hens

Studies have been made on interaction between rabbit antiserum to BB creatine kinase from hen gizzard and BB creatine kinases from the brain, heart and gizzard of hen. The degree of interaction was evaluated by the intensity of fluorescence of the immune complexes labeled by a fluorescent dye. It was shown that the intensity of fluorescence of the immune complexes formed by BB creatine kinases from the brain and gizzard of hen is approximately the same, whereas that formed by BB creatine kinase from the heart is twice lower. The data obtained indicate that structural differences in the region of antigenic determinants exist between BB creatine kinase from the heart and those from the brain and gizzard of hen.     

Highly Sensitive Immunoassay for Rat Brain-Type Creatine Kinase: Determination in Isolated Purkinje Cells

Ultrasensitive enzyme immunoassay method for the measurement of rat brain-type creatine kinase BB (CK-BB) was developed by use of purified antibodies specific to the B subunit of creatine kinase. The antibody immunoglobulin G was purified with immunoaffinity chromatography of the antiserum raised in rabbits by injecting the purified rat CK-BB. The assay system consisted of polystyrene balls with immobilized antibody F(ab')2 fragments and the same antibody Fab' fragments labeled with beta-D-galactosidase from Escherichia coli. The assay was specific to the B subunit of CK (CK-B), showing about 10% cross-reactivity with CK-MB, but it did not cross-react with CK-MM and neuron-specific gamma gamma enolase. The minimum detection limit of the assay was 0.1 pg or 1 amol CK-BB, being sufficiently sensitive for the measurement of CK-B contents in the isolated Purkinje cell bodies at the level of single cells. The average content of CK-B in a single Purkinje cell was 1.64 pg. The CK-B concentration in rat cerebellum (about 22 micrograms/mg protein) was about twofold higher than that (about 13 micrograms/mg protein) in the cerebrum. High levels (greater than 5 micrograms/mg protein) of CK-B were also found in the peripheral tissues such as gastrointestinal tract and urinary bladder, all of which are composed of smooth muscle. Immunohistochemical localization of CK-B antigens in the CNS revealed that the antigens is distributed not only in the neurons but also in the glial cells.     

Evolution of isozyme loci and their differential tissue expression

Summary The phylogeny of the creatine kinase (CK, EC 2.7.3.2) isozyme loci and their differential tissue expressions were determined for representatives of 65 families of vertebrates, with emphasis on the fishes. The transition from the single creatine kinase locus, characteristic of certain echinoderms, to the two creatine kinase loci which are orthologous to those present in all vertebrates, occurred early in the chordate line. The majority of pre-teleostean fishes possesses only these two CK loci (A and C). These loci are relatively generalized in their tissue expressions which are variable among species of primitive fishes. The third and fourth creatine kinase loci (B and D) arose separately in the ancestors of the bony fishes and appear to be the result of regional genome duplications. Concomitant with the increase in the number of isozyme loci has been an increase in the specificity of their tissue expression. In the advanced teleost fishes the four CK loci are differentially expressed in a characteristic manner. The A₂ isozyme predominates in skeletal muscle, the B₂ isozyme in eye and brain, the C₂ isozyme in stomach muscle, and the D₂ isozyme is found exclusively in testis. We propose a phylogeny of the creatine kinase genes in the lower chordates based on the time of appearance of new CK loci, the sequence in which the loci achieve a tissue restricted expression, and the immunochemical relatedness of the orthologous and paralogous gene products.     

Neurone-Specific Enolase and Creatine Phosphokinase Are Protein Components of Rat Brain Synaptic Plasma Membranes

Abstract: Neuron-specific enolase and creatine phosphokinase were found, by 2-dimensional gel analysis, in rat brain synaptic plasma membranes (SPM). The identity of these enzymes was confirmed by comigration with purified rat brain NSE and CPK and by peptide analysis. The specific enzymatic activities of enolase and creatine phosphokinase, as well as of pyruvate kinase, also present on the membranes, were comparable to those in the homogenates when these three enzymes were fully activated. In the SPM all three enzymes, particularly enolase, were partially cryptic in that enzymatic activities were very low unless the membranes were treated with Triton X-100. They were resistant to both low-salt and high-salt extraction and to trypsin, except when Triton X-100 was present. These results suggest that the enzymes are tightly bound protein components of the membrane and that they may constitute an assembly capable of generating ATP.