Characterization and regulation of heart adenosine 3':5'-monophosphate-dependent protein kinase isozymes.

There is broad species variation in the type of cAMP-dependent protein kinase isozyme present in supernatant fractions of heart homogenates as determined by DEAE-cellulose chromatography, Isozyme I, which elutes at less than 0.1 M NaCl, is predominant in mouse and rat hearts; while isozyme II, which elutes at greater than 0.1 M NaCl, is the predominant type in beef and guinea pig. Human and rabbit hearts contain about equal amounts of the two types. The type I heart kinases are more easily dissociated into free regulatory and catalytic subunits by incubation with histone than are the type II kinases, and the separated regulatory and catalytic subunits of isozyme II of rat heart reassociate more rapidly than the subunits of isozyme I under the conditions used. The data from several experiments using rat heart indicate that the basal activity ratio of the protein kinase in crude extracts (approximately 0.15) is due mainly to basal endogenous cAMP and that cAMP elevation accounts entirely for the epinephrine effect on the enzyme. Addition of epinephrine and 1-methyl-3-isobutylxanthine to the perfusate causes a rapid (1 min) increase in cAMP, active supernatant protein kinase, and active phosphorylase in perfused hearts of both rat (mainly isozyme I) and guinea pig (mainly isozyme II). The elevation percentage in cAMP is about the same in the two species, but the increase in active protein kinase is greater in rat heart. If hearts from either animal are perfused continually (10 min) with epinephrine (0.8 muM) and 1-methyl-3-isobutylxanthine (10 muM), the cAMP level, active protein kinase, and active phosphorylase remain elevated. Likewise, all parameters return rapidly to the basal levels when epinephrine and 1-methyl-3-isobutylxanthin are removed. Most of the epinephrine effect on the rat heart supernatant kinase is retained at 0 degrees if cAMP is removed by Sephadex G-25 chromatography, although this procedure completely reverses the epinephrine effect in the guinea pig heart. The epinephrine effect on the rabbit heart kinase (approximately equal amounts of isozymes I and II) is partially reversed by Sephadex G-25. These species differences can be accounted for by differences in association-dissociation behavior of the isozymes in vitro. The data suggest that epinephrine causes activation of both isozymes. The activity present in the particulate fraction comprises nearly half of the total cAMP-dependent protein kinase activity in homogenates of rabbit heart. Triton X-100 extracts of low speed particulate fractions from hearts of each species tested, including rat heart, contain predominantly or entirely the type II isozyme, suggesting differences in intracellular distribution of the isozymes. The binding of the protein kinase to the particulate fraction is apparently due to the properties of the regulatory subunit component. Differences in topographical distribution of the isozymes could provide for differences in either physiological regulation or substrate specificity.     

An electrophoretic analysis of the isozymes of malate dehydrogenase in several different plants

The particulate and soluble fractions of cell-free extracts from seeds, roots, and leaves of 10 different plants were examined electrophoretically for isozymes of malate dehydrogenase. Distinct isozyme patterns were observed for each plant and even for the individual tissues of each species. There were some isozymes in several different plant extracts with equal electrophoretic mobilities, but there was no isozyme band that was common to all tissues or to all plants.     

beta-Glucosidase of Penicillium funiculosum. I. Purification

A strain of Penicillium funiculosum, isolated in this laboratory, produced in high yield both endo- and exo-glucanases and beta-glucosidases, which were suitable for the saccharification of cellulosic materials. The isolation of the beta-glucosidase of this organism, which differs from other beta-glucosidases of fungi in its substrate specificity, by preparative electrophoresis, is described in this article. The organism was grown on a lactose-casein medium and the culture filtrate concentrated by ammonium sulfate precipitation and dialysis. Electrophoresis was carried out on large slabs of polyacrylamide gel in an anodicrun in the presence of borate at pH 7. After elution of active fractions, a cathodic run was made at pH 6.0. Two precipitations with ammonium sulfate resulted in a homogeneous enzyme (specific activity 174 IU/mg). A second isozyme was also produced by P. funiculosum on cellulose-wheat bran medium. This isozyme was purified by electrophoresis at pH 7.0 in the absence of borate and was obtained free from other isozymes of beta-glucosidase and cellulases.     

Preparation and characterization of two isozymes of choline acetyltransferase from squid head ganglia. II. Self-association, molecular weight determinations, and studies with inactivating antisera.

The two isozymes of choline acetyltransferase (Acetyl-CoA:choline O-acetyltransferase, EC 2.3.1.6) from head ganglia of Loligo pealei have been examined by polyacrylamide gel electrophoresis, gel chromatography, and equilibrium sedimentation in the ultracentrifuge. Inactivating antisera, prepared to both native and dithiothreitol-treated isozymes 1 and 2 of squid choline acetyltransferase, were used to demonstrate the immunologic identity of isozymes 1 and 2. Each isozyme appeared to contain two non-identical catalytically active subunits, with molecular weights of approx. 37 000 and 56 000. A staining method was developed to visualize choline acetyltransferase activity in acrylamide gels. The method is based on the formation of a precipitate of manganese ferrocyanide at sites where free coenzyme A is released. By this method, and by analysis of gel slices, it was found that each of the isozymes can form aggregates of several different sizes. The formation of immune precipitates with the aggregates showed the identity of the multiple bands of enzyme protein resolved on disc gel electrophoresis. Isozyme 1 was most active as a small aggregate, whereas isozyme 2 was most active as a large aggregate. Both chromatography on Sephadex G-200 and isoelectric focusing yielded a number of active species with molecular weights ranging from 35 000 to 300 000. In addition, we demonstrated the dissociation of enzyme protein in the presence of 1.0 - 10(-2) M dithiothreitol, the formation of multiple precipitin bands by aged enzyme, and the identity of the different isoelectric fractions of each of the isozymes.     

Further studies of primer-independent phosphorylase isozymes in the algae

Both Oscillatoria princeps and Cyanidium caldarium contain phosphorylase isozymes that can cause the synthesis of polyglucan from glucose-1-phosphate in the absence of added maltodextrin ‘primer’. In addition, O. princeps contains a primer-dependent phosphorylase isozyme. When the phosphorylase fractions isolated from extracts of the algae were treated with α-amylase, the primer-independent isozyme became primer-dependent and shifted from the position it was normally found at after polyacrylamide gel electrophoresis. This primer-independent isozyme became less mobile towards the anode, and was found at the locus usually occupied by the primer-dependent isozyme. It was not possible to restore its mobility towards the anode and its primer-independent properties by preincubation with maltoheptaose. The indication is that this isozyme is a glucoprotein and that the glucan component is chemically bonded to the protein.     

Comparison of Indole-3-acetic Acid Oxidation in Peroxidases from Rust-Infected Resistant Wheat Leaves

Seven peroxidase isozyme fractions were isolated from rust-infectedresistant wheat leaves by means of ammonium sulfate fractionation,pH precipitation, ion exchange chromatography and gel filtration.Three isozymes showed a single peroxidative band in the electrophoreticgels. The catalytic activity of the enzymes on non-physiologicalsubstrates was comparable to that of commercial horseradishperoxidase. When compared to isozyme 9, isozyme 10 had twicethe activity on guaiacol and eugenol but only one-fifth theoxidative activity on p-phenylenediamine and o-dianisidine.The IAA oxidation activity was compared among purified enzymefractions. Isozyme 10 was the only enzyme which could destroythe auxin without phosphate and manganese cofactors. All theother enzymes, including isozyme 9, showed the activity onlywhen both cofactors were present. The possible involvement ofthese peroxidases in IAA destruction in the resistant tissueis discussed. (Received June 14, 1984; Accepted October 15, 1984)     

Increased expression of protein kinase C isoforms in heart failure due to myocardial infarction

The activities of cardiac protein kinase C (PKC) were examined in hemodynamically assessed rats subsequent to myocardial infarction (MI). Both Ca(2+)-dependent and Ca(2+)-independent PKC activities increased significantly in left ventricular (LV) and right ventricular (RV) homogenates at 1, 2, 4, and 8 wk after MI was induced. PKC activities were also increased in both LV and RV cytosolic and particulate fractions from 8-wk infarcted rats. The relative protein contents of PKC-alpha, -beta, -epsilon, and -zeta isozymes were significantly increased in LV homogenate, cytosolic (except PKC-alpha), and particulate fractions from the failing rats. On the other hand, the protein contents of PKC-alpha, -beta, and -epsilon isozymes, unlike the PKC-zeta isozyme, were increased in RV homogenate and cytosolic fractions, whereas the RV particulate fraction showed an increase in the PKC-alpha isozyme only. These changes in the LV and RV PKC activities and protein contents in the 8-wk infarcted animals were partially corrected by treatment with the angiotensin-converting enzyme inhibitor imidapril. No changes in protein kinase A activity and its protein content were seen in the 8-wk infarcted hearts. The results suggest that the increased PKC activity in cardiac dysfunction due to MI may be associated with an increase in the expression of PKC-alpha, -beta, and -epsilon isozymes, and the improvement of heart function in the infarcted animals by imidapril may be due to partial prevention of changes in PKC activity and isozyme contents.     

Separation of SH-modified myosin subfragment-1 (A1) isozyme into two distinct equimolar fractions by an affinity chromatography

Our previous kinetic studies indicated that SH-modified myosin subfragment-1 A1 isozyme (S1(A1] contains at least two different types of active sites (Emoto, Y., Kawamura, T., & Tawada, K. (1985) J. Biochem. 98, 735-745). In those studies we have modified highly reactive SH-groups in S1(A1) with thimerosal. In this work, we separated the modified S1(A1) into two equimolar fractions by affinity chromatography with agarose-ADP. For the separation, Mg2+ in the elution buffer was indispensable. Although the two fractions appeared to have the same number of modified SH-groups per mol of S1, they had different enzymic and fluorescent properties. SH-modification with an excess of thimerosal for a much longer duration did not change any of the results: not the chromatographic profile, the properties of the two fractions, nor the number of modified SH-groups. Hence the two different populations were not generated by incomplete modification. After reduction with dithiothreitol, however, the differences between the two fractions disappeared. When we separately re-modified the reduced fractions and re-chromatographed them, in each case we again obtained two fractions, which had the same properties as the two fractions obtained from the original modification with thimerosal. These results demonstrate that the active site heterogeneity in SH-modified S1(A1) had no intrinsic origin in the unmodified S1: it was introduced by the SH-modification, but by an unknown mechanism(s) other than incomplete modification.     

A comparative study of the age-related patterns of decay of some nucleoside monophosphate kinases in human red cells

The nucleoside monophosphate kinases, adenylate kinase (AK), guanylate kinase (GUK), and uridine monophosphate kinase (UMPK), were studied electrophoretically and quantitatively in density gradient fractions of human red cells from normal adults which contain red cells of differing mean age. The enzymes were found to differ both in their rates and patterns of decay and in secondary isozyme formation during the life of the red cell in the circulation. AK showed no appreciable enzyme decay and slight genetation of secondary isozymes; UMPK showed a rapid monophasic decline and no secondary isozyme formation; GUK showed intermediate overall loss of activity with a biphasic pattern of decay and marked secondary isozyme formation. A comparative study of the two common phenotypes of UMPK (UMPK 1 and UMPK 2-1) and of AK (AK 1 and AK 2-1) was made. The UMPK 2 isozyme showed a more rapid decay than the UMPK 1 isozyme, whereas no difference was observed between the AK 1 and AK 2 isozymes.     

Developmental program of PGK-1 and PGK-2 isozymes in spermatogenic cells of the mouse: Specific activities and rates of synthesis

The specific activities and synthesis of the ubiquitous isozyme, PGK-1, and the testis-specific isozyme, PGK-2, have been quantitated and localized in spermatogenic cells of the mouse. There is a fivefold increase in total PGK specific activity between immature and adult testes which begins at approximately 30 days of age, coincident with the appearance of late-middle stage spermatids. The increase in total PGK is entirely due to the appearance and increase of the PGK-2 isozyme. Rates of PGK synthesis were measured by labeling testicular cells in vitro with [³H]leucine and purifying the PGK isozymes. When total testicular cells were examined, PGK-2 synthesis was detectable after 22 days of age at very low levels and increased in older testes to a level of 0.5% of total protein synthesis. PGK-1 synthesis remained relatively constant at all ages at a level 100-fold lower (0.005%). Testicular cells were separated into highly enriched fractions of particular spermatogenic stages by centrifugal elutriation. The PGK-1 synthesis rates were, again, very low and not significantly different between the various spermatogenic stages. PGK-2 synthesis was low to nondetectable in pachytene spermatocytes, increased to 0.07% in early spermatids and represented 0.7% of total protein synthesis in late spermatids. This increased rate of PGK-2 synthesis appears to require an increase in the amount of PGK-2 mRNA in late spermatids, cells in which no active RNA synthesis is detectable.     

Isoenzyme makeup of the malate dehydrogenase in 2 species of Acetabularia]

The isozymes of malate dehydrogenase (MDH) were studied by means of electrophoresis in polyacrilamide gel in Acetabularia crenulata and A. mediterranea. The isozyme profile of MDH was shown to be variable in different parts of the plant. Distinct differences in isozyme profiles of MDH between A. crenulata and A. mediteranea were found when studying the cell fractions which consisted mainly of chloroplasts. The chloroplast fraction of A. mediterranea contained 8 isozymes which form 2 groups with different electrophoretic mobility. The chloroplast fraction of A. crenulata contained 9 isozymes. All the isozymes of the first group were common for both the species under study.     

Selective expression of type I and type II cyclic AMP-dependent protein kinases in subcellular fractions of concanavalin A-stimulated rat thymocytes

Total protein kinase activity and the expression of the type I and type II cyclic adenosine 3′:5′-monophosphate-dependent protein kinases were studied in subcellular fractions of rat thymocytes and the effect of concanavalin A treatment on protein kinase activity was assessed. At a concentration of 100 μ/ml of concanavalin A a marked decline of total nuclear protein kinase activity occurred which lasted approximately 20 to 90 min. Concomitantly, a twofold increase of total protein kinase activity in the 900g supernatant fraction was observed which lasted from 5 to 30 min. Studies using the heat-stable protein kinase inhibitor revealed that the concanavalin A-mediated activity changes were primarily due to changes of cAMP-dependent protein kinase activity, whereas cAMP-independent protein kinase activity remained unchanged. Analysis of the type I and type II cAMP-dependent protein kinase isozyme pattern before and after concanavalin A treatment revealed a selective change of the relative expression of isozyme activities. Whereas type I protein kinase was the major nuclear isozyme before concanavalin A treatment, nuclear type II cAMP-dependent protein kinase increased markedly with a concomitant loss of type I isozyme expression. In the 900g supernatant fraction, containing primarily the type II isozyme in unstimulated cells, concanavalin A treatment caused an increase of the expression of the type I isozyme. The concanavalin A-mediated relative changes of cAMP-dependent protein kinase isozyme expression were confirmed by photoaffinity labeling of the regulatory subunits R^I and R^II before and after concanavalin A stimulation. The intracellular concanavalin A-mediated isozyme changes were time dependent, exhibiting maximal effects about 20 min after concanavalin A addition. These results indicate that selective regulation of intracellular cAMP-dependent protein kinase isozyme expression may be a mechanism related to isozyme-specific phosphorylation of specific intracellular substrates in concanavalin A-activated thymocytes.     

Analysis of glutathione S-transferase from human liver by isoelectric focusing in a urea minigel system.

A method for the rapid analysis of isozyme subunits of glutathione transferase (GST) from human liver is described. Following purification of enzyme protein to electrophoretic homogeneity on columns of GSH-agarose, pooled transferase fractions were concentrated by ultrafiltration and subjected to further fractionation and analysis by urea-isoelectric focusing in minigels using a Hoefer Mighty Small II electrophoresis system. These methods combined with immunoblotting techniques permitted the resolution, detection, and eventual analysis of up to six different subunits of the alpha isozyme of human GST and at least three to four different forms of the pi isozyme of the transferase rapidity, accuracy, and sensitivity of the methodology may prove useful to the analysis and quantification of GST subunits in biopsies of malignant human tissue and to the development of effective chemotherapeutic regimens.     

Variations in the response of mouse isozymes of adenylosuccinate synthetase to inhibitors of physiological relevance

Vertebrates have acidic and basic isozymes of adenylosuccinate synthetase, which participate in the first committed step of de novo AMP biosynthesis and/or the purine nucleotide cycle. These isozymes differ in their kinetic properties and N-leader sequences, and their regulation may vary with tissue type. Recombinant acidic and basic synthetases from mouse, in the presence of active site ligands, behave in analytical ultracentrifugation as dimers. Active site ligands enhance thermal stability of both isozymes. Truncated forms of both isozymes retain the kinetic parameters and the oligomerization status of the full-length proteins. AMP potently inhibits the acidic isozyme competitively with respect to IMP. In contrast, AMP weakly inhibits the basic isozyme noncompetitively with respect to all substrates. IMP inhibition of the acidic isozyme is competitive, and that of the basic isozyme noncompetitive, with respect to GTP. Fructose 1,6-bisphosphate potently inhibits both isozymes competitively with respect to IMP but becomes noncompetitive at saturating substrate concentrations. The above, coupled with structural information, suggests antagonistic interactions between the active sites of the basic isozyme, whereas active sites of the acidic isozyme seem functionally independent. Fructose 1,6-bisphosphate and IMP together may be dynamic regulators of the basic isozyme in muscle, causing potent inhibition of the synthetase under conditions of high AMP deaminase activity.     

荞麦属植物淀粉酶和甲酸脱氢酶同功酶研究(英文)

以聚丙烯酰胺凝胶电泳方法研究了荞麦属植物8个种42个收集系干种子和发芽种子的淀粉酶和甲酸脱氢酶同功酶。结果表明,荞麦淀粉酶在于种子中缺乏活性,但是在发芽种子中活性很强。在供试材料的发芽种子中共发现23个淀粉酶谱带,其中甜荞和苦荞分别有10条和8条。不同荞麦种间淀粉酶谱带差异很大,但是同种内不同收集系间差异较小。谱带聚类分析表明大野荞和毛野荞分别与甜荞和苦荞较近缘,支持它们分别为甜荞和苦荞祖先种的假说。在干种子和发芽种子中,发现所有荞麦种类均只有1条位置一致的甲酸脱氢酶谱带,暗示该酶在进化中具有高度稳定性。     

Properties of Alkaline Phosphatase in Cucumber Roots Induced by Calcium Starvation

Calcium deficiency caused an increase in alkaline phosphataseactivity in cucumber roots [Matsumoto and Yamaya (1981) Plant& Cell Physiol. 22: 1137]. The activities of other hydrolasesincluding acid phosphatase, nucleases and proteases, however,were much less affected by the removal of calcium. Nucleosidedi- and triphosphates and inorganic pyrophosphate were effectivelyhydrolyzed by the induced alkaline phosphatase, whereas nucleosidemonophosphate-hydrolyzing activity was basically equal in theroots grown with either complete medium or a medium lackingcalcium. The alkaline phosphatase in cucumber roots was foundin fractions pelleting at 3,000 x g and in the 100,000 x g supernatant.The calcium-starved roots increased their alkaline phosphataseactivity in both fractions. Four isozyme bands of the alkalinephosphatase in the soluble fraction were separated by polyacrylamidegel electrophoresis. One of the isozyme bands showed a prominentincrease with the calcium deficiency, but not in the presenceof cycloheximide. (Received June 24, 1981; Accepted September 3, 1981)     

Multiplicity of progesterone 21-hydroxylase activities associated with constitutive forms of rabbit liver cytochrome P-450

Constitutive cytochromes P-450 have been solubilized from untreated outbred New Zealand White rabbit liver microsomes. Gradient phosphate buffer elution of DEAE-cellulose columns partially resolved six P-450 fractions. Progesterone 21-hydroxylase activity was reconstituted with several fractions and inhibited by an antibody towards P-450 Form 1. One fraction (LM3b) preferentially catalysed the 6 beta- and 16 alpha-hydroxylation of progesterone. SDS-PAGE indicated the presence of proteins with mobilities closely related to Form 1 in several fractions that were separated from this isozyme by DEAE-cellulose chromatography. These results suggest that several constitutive P-450 fractions may contribute to the regiospecific 21-hydroxylation of progesterone.     

Mutations in genes cpxA and cpxB of Escherichia coli K-12 cause a defect in isoleucine and valine syntheses.

Mutations in two chromosomal genes of Escherichia coli, cpxA and cpxB, produced a temperature-sensitive growth defect that was remedied specifically by the addition of isoleucine and valine to the minimal medium. This auxotrophy was manifested only when the medium contained exogenous leucine, suggesting that mutant cells fail to elaborate active acetohydroxy acid synthase, isozyme I. In the presence of leucine, this enzyme was required to catalyze the first reaction common to the biosynthesis of isoleucine and valine. Measurements of enzyme activity in crude extracts showed that mutant cells were seven- to eightfold deficient in active isozyme I when the cells were grown in the presence of leucine. When grown in the absence of leucine, mutant cells contained more acetohydroxy acid synthase activity. We attribute this activity to isozyme III, the product of the ilvHI genes, which are derepressed in the absence of exogenous leucine. The cpxA and cpxB mutations appear to affect the production of active isozyme I, rather than its activity, since (i) neither the cpxA nor the cpxB gene mapped near the structural gene for isozyme I (ilvB), (ii) the growth of mutant cells shifted from the permissive (34 degrees C) to the nonpermissive (41 degrees C) temperature did not immediately cease, but declined gradually over a period corresponding to several normal generation times, and (iii) the enzyme from mutant cells grown at 34 degrees C was as stable at 41 degrees C as the enzyme from cpx+ cells.     

Nuclear location of phosphoglycerate mutase BB isozyme in rat tissues.

We have previously reported (Ure?a et al. Eur. J. Cell Biol. 1990) that in skeletal muscle, type MM phosphoglycerate mutase isozyme is present in the nucleus as well as in the cytosol. To determine whether type BB phosphoglycerate mutase isozyme is also present in nucleus, the subcellular location of this isozyme was studied in different rat tissues by cell fractionation and immunogold techniques. With the aid of high affinity-purified anti-phosphoglycerate mutase BB isozyme antibodies, the isozyme was located in the nucleus of neuronal, astroglial and liver cells but not in the nucleus of oligodendroglial and endothelial cells. Biochemical studies on purified nuclear fractions also demonstrated the presence of phosphoglycerate mutase activity in the nucleus. Both immunocytochemical and biochemical techniques showed that nuclear phosphoglycerate mutase-specific activity depended on the type of cell.     

Isozymes of Ipomoea batatas catechol oxidase differ in catalase-like activity.

The amino acid sequences of two isozymes of catechol oxidase from sweet potatoes (Ipomoea batatas) were determined by Edman degradation of BrCN cleavage fragments of the native protein and by sequencing of amplified cDNA fragments. Sequence alignment and phylogenetic analysis of plant catechol oxidases revealed about 80% equidistance between the two I. batatas catechol oxidases and approximately 40--60% to catechol oxidases of other plants. When H(2)O(2) was applied as substrate the 39 kDa isozyme, but not the 40 kDa isozyme, showed catalase-like activity. The structure of the 40 kDa isozyme was modeled on the basis of the published crystal structure of the 39 kDa isozyme [T. Klabunde et al., Nat. Struct. Biol. 5 (1998) 1084]. The active site model closely resembled that of the 39 kDa isozyme determined by crystallography, except for a mutation of Thr243 (40 kDa isozyme) to Ile241 (39 kDa isozyme) close to the dimetal center. This residue difference affects the orientation of the Glu238/236 residue, which is thought to be responsible for the catalase-like activity of the 39 kDa isozyme for which a catalytic mechanism is proposed.