The early ontogeny of digestive and metabolic enzyme activities in two commercial strains of arctic charr (Salvelinus alpinus L.)

The extent to which growth performance is linked to digestive or energetic capacities in the early life stages of a salmonid species was investigated. We compared two strains of Arctic charr known to have different growth potentials during their early development (Fraser and Yukon gold). Trypsin, lipase, and amylase activities of whole alevins were measured at regular intervals from hatching through 65 days of development. To assess catabolic ability, we also measured five enzymes representing the following metabolic pathways: amino acid oxidation (amino aspartate transferase), fatty acid oxidation (beta-hydroxy acyl CoA-dehydrogenase), tricarboxylic acid cycle (citrate synthase), glycolysis (pyruvate kinase), and anaerobic glycolysis (lactate dehydrogenase). The measurement of these enzyme activities in individual fish allowed a clear evaluation of digestive capacity in relation to energetic demand. We also compared triploid and diploid individuals within the Yukon gold strain. For the whole experimental period, diploid Yukon gold fish exhibited the highest growth rate (1.08+/-0.18% length/day) followed by triploid Yukon gold fish (1.00+/-0.28% length/day) and finally Fraser strain fish (0.84+/-0.28% length/day). When differences in enzyme activities were observed, the Fraser strain showed higher enzyme activities at a given length than the Yukon gold strain (diploid and triploid). Higher growth performance appears to be linked to lower metabolic capacity. Our results suggest that fish may have to reach an important increase in the ratio of digestive to catabolic enzyme activities or a leveling off of metabolic enzyme activities before the onset of large increases in mass.

Pyruvate kinase type tumor M2 in urological malignancies

INTRODUCTION

The dimeric form of pyruvate kinase type M2 is overexpressed in tumor cells (TuM2-PK). The aim of the present study was to evaluate the clinical value of TuM2-PK as a tumor marker for renal cell carcinoma (RCC), transitional cell carcinoma of the bladder (TCC) and prostate cancer (PCA) by using a commercially available enzyme-linked immunosorbent assay for detection of TuM2-PK in plasma.

MATERIAL AND METHODS

The TuM2-PK concentration in EDTA plasma was determined quantitatively and immunologically using an ELISA (ScheBoTech, Germany). We measured the TuM2-PK plasma levels of 83 patients with RCC, 30 patients with TCC and 30 patients with PCA before any therapy. 100 patients with various non-malignant urological disorders were recruited as the control group.

RESULTS

Only patients with RCC showed significantly elevated plasma levels of TuM2-PK compared to the control group (p < 0.01). We found a sensitivity of 42.6% and a specificity of 80.4% using a cut-off value of 15 U/ml (manufacturer's recommendation). During follow-up, only 50% showed increasing plasma levels of TuM2-PK in case of metastases. Significant differences could not be detected in either TCC or PCA.

CONCLUSIONS

Our data suggest that TuM2-PK is not a useful marker for TCC and PCA. Due to low sensitivity and specificity, TuM2-PK is not suitable for the diagnosis of RCC. Whether TuM2-PK may be useful in advanced RCC to control success of palliative treatment regimens is still unclear.

Measurement of fecal pyruvate kinase type M2 (tumor M2-PK) concentrations in patients with gastric cancer, colorectal cancer, colorectal adenomas and controls

BACKGROUND

The determination of Tumor M2 Pyruvate Kinase (Tumor M2-PK) in EDTA plasma has been described as a tumor marker in a variety of different tumor types. Since most GI tumors grow intraluminally, it appeared interesting to determine whether Tumor M2-PK is detectable in the feces of tumor patients.

MATERIALS AND METHODS

Measurements were performed with a commercially available ELISA (ScheBo Biotech AG, Giessen, Germany) modified for fecal analysis. Samples of controls, GI cancer and adenoma patients were tested.

RESULTS

Fecal Tumor M2-PK concentrations could be quantified. A significant difference between cancer patients and controls was found. The highest concentrations were observed in colorectal cancer. However, fecal Tumor M2-PK was not detectable in 5 tumor patients.

CONCLUSION

The measurement of fecal Tumor M2-PK concentrations might provide an interesting screening tool for colorectal cancer. Further studies comparing the determination of Tumor M2-PK in stool to occult blood in stool are in progress.

A method for activity staining after native polyacrylamide gel electrophoresis using a coupled enzyme assay and fluorescence detection: application to the analysis of several glycolytic enzymes

We describe a method for the detection of isoforms of several glycolytic enzymes by activity staining after native PAGE. The staining is based on coupled enzyme assays carried out on the gel after electrophoresis and is linked to the disappearance of NADH, which is visualized by fluorescence. This method offers reliable and sensitive detection for phosphoenolpyruvate carboxylase, PPi-dependent phosphofructokinase, and pyruvate kinase from plant tissues. It can be applied to the detection of all enzymes which are normally detected spectrophotometrically using coupled enzyme assays consuming NAD(P)H.

Cross-talk between the signals hypoxia and glucose at the glucose response element of the L-type pyruvate kinase gene

The signals oxygen and glucose play an important role in metabolism, angiogenesis, tumorigenesis, and embryonic development. Little is known about an interaction of these two signals. We demonstrate here the cross-talk between oxygen and glucose in the regulation of L-type pyruvate kinase (L-PK) gene expression in the liver. In the liver the periportal to perivenous drop in O(2) tension was proposed to be an endocrine key regulator for the zonated gene expression. In primary rat hepatocyte cultures the expression of the L-PK gene on mRNA and on protein level was induced by venous pO(2), whereas its glucose-dependent induction occurred predominantly under arterial pO(2). It was shown by transient transfection of L-PK promoter luciferase and glucose response element (Glc(PK)RE) SV40 promoter luciferase gene constructs that the modulation by O(2) of the glucose-dependent induction occurred at the Glc(PK)RE in the L-PK gene promoter. The reduction of the glucose-dependent induction of the L-PK gene expression under venous pO(2) appeared to be mediated via an interference between hypoxia inducible factor-1 (HIF-1) and upstream stimulating factor at the Glc(PK)RE. The glucose response element also functioned as an hypoxia response element which was confirmed in cotransfection assays with Glc(PK)RE luciferase gene constructs and HIF-1alpha expression vectors. Furthermore, it was found by gel shift and supershift assay that HIF-1alpha and USF-1 or USF-2 could bind to the Glc(PK)RE. Our findings implicate that the cross-talk between oxygen and glucose might have a fundamental role in the regulation of several physiological and pathophysiological processes.

Tungstate is an effective antidiabetic agent in streptozotocin-induced diabetic rats: a long-term study

AIMS/HYPOTHESIS

Recent studies have shown the anti diabetic effects of oral sodium tungstate treatment in several animal models of diabetes based on short-term experiments. In this study, we examined the effectiveness of long-term tungstate treatment of streptozotocin-induced-diabetic rats.

METHODS

Tungstate was administered to the drinking water of rats for eight months.

RESULTS

The treatment resulted in a reduction in serum glucose concentrations in diabetic rats, but no change in glycaemia was detected in healthy rats. Alterations in the hepatic glucose metabolism due to diabetes were almost completely counteracted by tungstate treatment. The partial recovery of glucokinase activity, not found in diabetic animals, normalised glycogen and glucose 6-phosphate concentrations. Tungstate treatment also restored pyruvate kinase activity and fructose 2,6-bisphosphate concentrations. In healthy rats, tungstate treatment did not modify the majority of the hepatic parameters studied. Moreover, tungstate treatment prevented diabetes-induced morphological changes in the kidney and ocular lens and also reduced mortality. Furthermore, no hypoglycaemic episodes or undesirable side effects were observed in treated diabetic or healthy rats. In addition, there is no evidence of intolerance developing after prolonged use.

CONCLUSION/INTERPRETATION

Tungstate could play a helpful part in the long-term treatment of diabetes.

Anemia, splenomegaly, and increased osmotic fragility of erythrocytes in Abyssinian and Somali cats

OBJECTIVE

To determine clinical and clinicopathologic features of a chronic intermittent severe hemolytic anemia characterized by erythrocyte osmotic fragility in Abyssinian and Somali cats.

DESIGN

Case series.

ANIMALS

13 Abyssinian and 5 Somali cats.

PROCEDURES

History, pedigree information, and results of routine laboratory tests, special erythrocyte studies, and histologic evaluation of splenic and hepatic specimens were analyzed.

RESULTS

Age at which clinical signs of anemia were first apparent ranged from 6 months to 5 years. Ten cats had splenomegaly. Most often, the PCV was between 15 and 25%, but it was as low as 5% at some times. The anemia was characterized by macrocytosis and mild to moderate reticulocytosis, but no poikilocytosis. Hyperglobulinemia, lymphocytosis, mild hyperbilirubinemia, and high hepatic enzyme activities were common findings. Results of Coombs tests and tests for infectious diseases were negative. The erythrocytic osmotic fragility was high in affected cats (mean osmotic fragility, 0.66 to 0.78%), compared with healthy cats (0.48 to 0.58). No specific membrane protein abnormality, erythrocyte enzyme deficiency, or hemoglobinopathy was identified. Histologic evaluation of splenic and hepatic specimens revealed extramedullary hematopoiesis and hemosiderosis. Four of the 5 Somali cats were closely related.

CONCLUSIONS AND CLINICAL RELEVANCE

On the basis of results of pedigree analyses, the apparent breed predilection, and the exclusion of other known causes of anemia in cats, we believe that the hemolytic anemia in these cats was likely a result of a novel hereditary erythrocyte defect. A genetic predisposition to immune-mediated destruction of erythrocytes could not be ruled out.

The tumor marker tumor M2-PK: an application in the diagnosis of gastrointestinal cancer

The present study is designed to evaluate the use of the tumor marker Tumor M2-PK in the discrimination between gastrointestinal (Gl) cancer patients and patients with non malignant gastrointestinal diseases. The concentration of Tumor M2-PK was analyzed in EDTA-plasma of 413 Gl cancer-patients and 141 patients with non-malignant diseases. The test resulted in a highly significant discrimination (p < 0.001) of tumor patients and controls. The diagnostic specificity was 89%. A diagnostic sensitivity between 48% and 73%, depending on the different tumor entities (colorectal cancer, gastric cancer, oesophageal cancer and pancreatic cancer), was observed. These sensitivities were generally higher when compared with those of the established tumor markers CEA, CA 19-9 and CA 72-4, with the exception of CA 19-9 in pancreatic cancer. A combination of Tumor M2-PK with the appropriate first choice-marker (e.g. CEA + Tumor M2-PK for colorectal cancer) resulted in a remarkable increase in the sensitivities.

Tumor M2-pyruvate kinase: a promising tumor marker in the diagnosis of gastro-intestinal cancer

The diagnostic value of pyruvate-kinase type tumor M2 (Tumor M2-PK) has been investigated in different tumors, and showed interesting results in cases of renal cancer, pancreatic cancer, lung cancer and some cases of gastric cancer. In this study we investigated EDTA-plasma of 68 patients with gastrointestinal cancer, 22 patients with inflammatory bowel disease (IBD) and 60 healthy controls. Sensitivity of Tumor M2-PK was 70.6% for all GI-tumors, that of CA19-9 was 55.4% and that of CEA was 53.3%. In pancreatic cancer CA19-9 showed the best sensitivity. In oesophageal/gastric cancer Tumor M2-PK was most sensitive and in colorectal cancer CEA and Tumor M2-PK showed the best results. The specificity of Tumor M2-PK was 90-96, 7%. In IBD some individuals showed elevated Tumor M2-PK levels but there was no correlation to CRP or to the clinical activity score. The results indicated that Tumor M2-PK might be a valuable marker in gastrointestinal cancer.

Cross-species identification of novel Candida albicans immunogenic proteins by combination of two-dimensional polyacrylamide gel electrophoresis and mass spectrometry

We have previously reported the usefulness of two-dimensional gel electrophoresis followed by Western blotting with sera from patients with systemic candidiasis in the detection of the major Candida albicans antigens (Pitarch et al., Electrophoresis 1999, 20, 1001-1010). The identification of these antigens would be useful for the characterization of good markers for the disease, and for the development of efficient diagnostic strategies. In this work we have used nanoelectrospray tandem mass spectrometry to obtain amino acid sequence information from the immunogenic proteins previously detected. We report here the cross-species identification of these antigens by matching of tandem mass spectrometry data to Saccharomyces cerevisiae proteins. Using this approach, we unambiguously identified the four C. albicans immunogenic proteins analyzed, namely aconitase, pyruvate kinase, phosphoglycerate mutase and methionine synthase. Furthermore, we report for the first time that aconitase, methionine synthase and phosphoglycerate mutase have antigenic properties in C. albicans.

[Renal cell carcinoma. Immunohistological study to the expression of the inactive form of the pyruvate kinase]

PURPOSE

The inactive form of pyruvatekinase could be established in different tumours. Purpose of this study was to demonstrate the presence or absence of the inactive form of pyruvatekinase in renal cell carcinoma, metastases and benign renal tissue by immunohistology.

METHOD

After deparaffinization of formaline-fixed tissue (5 original tumours, 2 metastases and 5 benign renal tissues) cells were stained (APAAP-method) with Clon DF4 (ScheBo Tech).

RESULTS

All malign tissue showed a positive reaction, inside benign tissue we saw a positive reaction of endothelial cells however we saw no reaction with benign renal cells.

CONCLUSION

Renal cell carcinoma and metastatic cells show a strong immunohistological reaction against the inactive form of pyruvatekinase, no reaction of benign renal cells. It should be possible to develop a serological tumour marker for renal cell carcinoma.

Hypoxic response of synaptosomal proteins in term guinea pig fetuses

Early events in the hypoxia-induced response trigger tyrosine phosphorylation cascades involving a large number of enzymes and substrates. The resolving power of advanced two-dimensional gel electrophoresis, followed by immunoblotting with specific antibodies to phosphotyrosine, has been used to analyze hypoxia-induced modifications in guinea pig brain synaptosomes. These procedures, in conjunction with computer-aided image analysis, are useful in the differential display of gene products, providing comparison at the level of posttranslationally modified products. Studies were performed in cerebral cortical synaptosomes from three normoxic and three hypoxic newborn guinea pigs. To filter off background noise consisting of nonreproducible migrating protein spots, only reproducible features of electrophoretic patterns were considered. Immunoreactivity patterns obtained with anti-phosphotyrosine antibodies proved to be different in normoxic and hypoxic synaptosomes: of a total of 130 immunoreactive spots, 49 were tyrosine-phosphorylated in hypoxic synaptosomes only and 20 in the normoxic ones only. Our data suggest that hypoxia extensively remodels the signaling pathway by switching off tyrosine phosphorylation of some cellular components (i.e., alpha-internexin) and switching on tyrosine phosphorylation of some other proteins (i.e., heat shock cognate 70, aconitase, 2',3'-cyclic nucleotide 3'-phosphodiesterase, and pyruvate kinase).

Clinical and genetic studies of Japanese homozygotes for the Gaucher disease L444P mutation

In patients originally genotyped as homoallelic for the Gaucher disease (GD) L444P (1448C) mutation, we sought to confirm previously reported phenotypic differences between Caucasians and Japanese, to determine the prevalence and phenotypic impact of recombinant alleles, and to explore the phenotypic influence of genetic background. We therefore analyzed data from longer-term clinical follow-up, more comprehensive genotyping and polymorphism and mitochondrial DNA (mtDNA) testing in all known Japanese L444P homozygotes (n=15). Our studies demonstrated that, of 12 patients in our series originally diagnosed with non-neuronopathic GD, 9 developed neurological signs/symptoms during follow-up (at a mean of 14 years 11 months +/- 11 years 4 months). Of three patients originally diagnosed with acute neuronopathic (type 2) GD, all three were compound heterozygotes for L444P and the complex allele RecNci I. In the entire series, Pvu II and liver erythrocyte pyruvate kinase (PKLR) polymorphism and prevalence of the 9 bp mtDNA deletion were heterogeneous, and these background genetic factors could not predict phenotypic expression. Our data suggest that, in Japanese as in Caucasian patients, the L444P/L444P genotype is highly associated with subacute neuronopathic (type 3) GD, and the presence of a complex allele together with an L444P allele leads to type 2 disease. Our findings also underline the importance of comprehensive genotyping (particularly testing for recombinant alleles), long-term follow-up and careful neurological examination in patients with early-onset GD. Such measures ultimately may improve genotype/phenotype correlations and, with them, genetic counseling and therapeutic decision making.

Marker for renal cell carcinoma (RCC): the dimeric form of pyruvate kinase type M2 (Tu M2-PK)

OBJECTIVE

The evaluate a potential tumor marker for RCC. Tumor formation is generally linked to an expansion of glycolytic phosphometabolite pools and aerobic glycolyticflux rates. To achieve this, tumor cells generally overexpress a special glycolytic isoenzyme, termed pyruvate kinase type M2. To establish the expansion of phosphometabolite pools pyruvate kinase switches between a tetrameric form with high phosphoenol-pyruvate (PEP) affinity and a dimeric form with a lower PEP affinity. The dimeric form is predominant in all tumors that have been investigated and has been termed TuM2Pk.

MATERIALS AND METHODS

We studied: a) the expression of TuM2Pk in RCC by immunohistochemistry using a monoclonal antibody recognizing only the mono- or dimeric form of pyruvate kinase, b) the stability of TuM2Pk in serum by measuring TuM2Pk in 3 patients at different times after taking blood with a two-site immunometric assay, c) the a circadiane rhythm of TuM2Pk in blood by measuring levels every 4 hours in 5 patients, d) TuM2Pk- expression in serum (see 2.) in 5 patients by taking blood from tumor-side vena renalis compared to peripherally blood, e) TuM2Pk (see point 2.) in 40 RCC-patients comparing the results with 39 healthy persons and clinical data of RCC, f) the influence of wound healing to TuM2Pk by measuring serum-levels during a period of more than 12 weeks in 6 patients, g) the individual follow up of 4 patients with RCC stage Robson III for more than 2 years. Comparing TuM2Pk-levels to findings of staging by computed tomography.

RESULTS

The isoenzyme TuM2Pk could be demonstrated in RCC and their metastases by immunohistochemistry with a monoclonal antibody specific for pyruvate kinase type M2. In normal kidney cells pyruvate kinase type M2 is not detectable. The stability of TuM2Pk was studied in the serum within 30 minutes. No circadian rhythm was found. Most serum TuM2Pk comes from tumor. Serum evaluation in 39 healthy persons was used to determine normal values, with an upper concentration of 28 U/ml of TuM2Pk (95% percentile of normal healthy persons). Serum evaluation in 40 RCC showed a significant difference to healthy persons and a positive correlation with Robson stage and grading No correlation of TuM2Pk was found with histopathological cell type of tumor diameter. After radical nephrectomy normalization of TuM2Pk level was found within 11 weeks in all localized RCC. Continuously elevated serum levels were seen in metastatic RCC. Individual follow-up seems to be possible.

CONCLUSION

Initial discrimination is not possible between localized and metastasized RCC using TuM2PK; however, it is possible to differentiate between benign and malignant renal processes; the specificity under these circumstances is 75%. After successful surgery of localized RCC, an elevated TuM2Pk will be normalized within 11 weeks, and will be remain elevated or will increase again in case of RCC-relapse or metastasis. Thus TuM2Pk would appear to be a useful marker for RCC detection and follow-up.

Quantitative detection of tumor M2-PK in serum and plasma

The majority of tumors express an isoform of the glycolytic enzyme pyruvate kinase, the type tumor M2. The isoenzyme exists in an active tetrameric and a less active dimeric form. The dimeric form is strongly overexpressed in tumor cells and this new tumor marker is thus called tumor M2-PK. This isoenzyme is released from tumor cells and is quantitatively detectable in body fluids by a sensitive enzyme-linked immunosorbent assay (ELISA). To establish the ELISA for the routine diagnostic in a clinical laboratory, the sample stability was evaluated. Therefore, blood samples were collected in different ways from healthy donors. Reproducibility of tumor M2-PK detection in EDTA-plasma was not affected by the day to day 'stress' in a clinical routine (e.g. shaking, leaving the samples at room temperature for several hours without prior centrifugation). Similar results were obtained with citrate-plasma, whereas detection in serum and heparin-plasma was only reproducible when the blood samples were centrifuged within 2 hrs after collection. It appears that lymphocytes contain small amounts of the tumor M2-PK isoenzyme. They might release tumor M2-PK in heparin-plasma and serum samples, but not in EDTA-plasma samples. The results indicated that EDTA-plasma appears to be most appropriate for the routine diagnostic of tumor M2-PK as a tumor marker.

Reversible phosphorylation control of skeletal muscle pyruvate kinase and phosphofructokinase during estivation in the spadefoot toad, Scaphiopus couchii

Both pyruvate kinase (PK) and phosphofructokinase (PFK) occur in two different forms, separable by isoelectric focusing (IEF), in skeletal muscle of the spadefoot toad Scaphiopus couchii. During estivation (aerobic dormancy) the proportions of the two forms changed compared with controls; in both cases the amount of enzyme in Peak I (pI = 5.3-5.4) decreased whereas activity in Peak II (isoelectric point = 6.2-6.4) increased. In vitro incubation of crude muscle extracts with 32P-ATP under conditions that promoted the activity of cAMP-dependent protein kinase led to strong radiolabeling associated with Peak I, but not Peak II, and reverse phase HPLC confirmed that 32P was associated with the subunits of both PK and PFK found in Peak I. Specific radiolabeling of Peak I PK and PFK by protein kinase A was further confirmed using immunoprecipitation. In total, this information allowed identification of the Peaks I and II enzymes as the phosphorylated and dephosphorylated forms, respectively, and the effect of estivation was to increase the proportion of dephosphorylated PK and PFK in muscle. Analysis of the kinetic properties of partially purified PK and PFK revealed significant kinetic differences between the two forms of each enzyme. For PK, the Peak II (low phosphate) enzyme showed a 1.6-fold higher Km for phosphoenolpyruvate and a 2.4-fold higher Ka for fructose-1,6-bisphosphate than did the Peak I (high phosphate) form. These kinetic properties suggest that Peak II PK is the less active form, and coupled with the shift to predominantly the Peak II form during estivation (87% Peak II vs. 13% Peak I), are consistent with a suppression of PK activity in estivating muscle, as part of the overall metabolic rate depression of the estivating state. A similar shift to predominantly the Peak II, low phosphate, form of PFK (75% Peak II, 25% Peak I) in muscle of estivating animals is also consistent with metabolic suppression since phosphorylation of vertebrate skeletal muscle PFK is typically stimulated during exercise to enhance enzyme binding to myofibrils in active muscle. Peak II PFK also showed reduced sensitivity to inhibition by Mg:ATP (I50 50% higher) compared with the Peak I form suggesting that the enzyme in estivating muscle is less tightly regulated by cellular adenylate status than in awake toads. The data indicate that reversible phosphorylation control over the activity states of enzymes of intermediary metabolism is an important mechanism for regulating transitions between dormant and active states in estivating species.

Effect of centrifugation at 2G for 14 days on metabolic enzymes of the tibialis anterior and soleus muscles

BACKGROUND

The enzyme composition of different muscle types vary greatly, leading to different changes of enzyme level caused by exposure to various stimuli.

METHODS

Male Wistar rats were centrifuged at 2G in a 12-ft radius centrifuge for 14 d. Tibialis anterior (TA) and soleus muscles from four centrifuge and four control rats were analyzed for three enzymes characteristic of fast twitch muscles (phosphofructokinase, glycerol-3-phosphate dehydrogenase, and pyruvate kinase), and four enzymes characteristic of slow twitch muscles (hexokinase, mitochondrial thiolase, B-hydroxyacyl CoA dehydrogenase, and citrate synthase).

RESULTS

The centrifuged TA muscles lost 15% of their weight; the corresponding soleus muscles gained 4%. Calculated on the basis of dry weight, the fast twitch enzyme activities were reduced 3-15% in the TA muscles but increased 10-23% in the soleus muscles. The slow twitch enzymes were reduced 18-30% in TA muscles but were almost unchanged in the soleus muscles. When calculated on the basis of total muscle weight, all of the enzymes in TA muscles were significantly reduced by centrifugation. In contrast, in soleus muscles, on the basis of total muscle weight, centrifugation caused an average increase of 22% in the fast twitch enzymes but only marginal changes in the slow twitch enzymes.

Using the yeast two-hybrid system to identify human epithelial cell proteins that bind gonococcal Opa proteins: intracellular gonococci bind pyruvate kinase via their Opa proteins and require host pyruvate for growth

Neisseria gonorrhoeae opacity-associated (Opa) proteins are a family of outer membrane proteins involved in gonococcal adherence to and invasion of human cells. We wanted to identify additional roles for Opa in the infectious process and used the yeast two-hybrid system to identify human epithelial cell proteins that interact with Opa proteins. Although this system has been used successfully to identify many types of interacting proteins, it has not been used to screen a human cell cDNA library for binding partners of a prokaryotic outer membrane protein. Therefore, we were also interested in exploring the versatility of the yeast two-hybrid system in identifying bacteria-host interactions. Using OpaP from strain F62SF as bait, we screened a HeLa cell cDNA library for Opa-interacting proteins (OIPs). We identified five different OIPs, designated OIP1-OIP5, two of which are homologous to human proteins--thyroid hormone receptor interacting protein (TRIP6) and pyruvate kinase isoenzyme M2 (PK). In the studies presented here, we investigated the interaction between Opa proteins and PK in more depth. Opa-PK interactions were confirmed by in vitro and in vivo assays independent of the yeast two-hybrid system. Escherichia coli expressing six different Opa proteins from gonococcal strain FA1090 all bound more PK than Opa-negative E. coli in in vitro binding assays. Using anti-PK antibody and fluorescence microscopy, we showed that human epithelial cell PK co-localizes with intracellular Opa+ gonococci and E. coli expressing Opa proteins. Using a mutant of N. gonorrhoeae unable to grow on pyruvate or lactate, it appears that intracellular pyruvate is essential for gonococcal growth and survival. These results suggest a novel mechanism in bacterial pathogenesis, i.e. the requirement for direct molecular interaction with a host metabolic enzyme (PK) for the acquisition of an essential intracellular carbon source and growth substrate (pyruvate). These results demonstrate that the yeast two-hybrid system is a valuable tool for identifying biologically relevant interactions between bacteria and host proteins, providing valuable leads for further investigations into novel mechanisms of bacterial pathogenesis.

N-acetylneuraminic acid, phosphate and thiol groups of pyruvate kinase isoenzymes from Morris hepatoma 7777 and normal rat liver

The highest amount of N-acetylneuraminic acid (AcNeu) was found in pyruvate kinase isoenzyme L from normal rat liver (24 moles/mole of enzyme tetramer), with the highest electrophoretic mobility. On the other hand, isoenzyme M2 from Morris hepatoma 7777, with the lowest electrophoretic mobility, had the lowest AcNeu content (5 moles/mole of enzyme tetramer). This tumour isoenzyme M2 of pyruvate kinase was, however, characterised by the highest phosphate content (12 moles/mole protein), in comparison to isoenzyme L (3 moles/mole protein) or normal liver isoenzyme M2 (6 moles/mole protein). This could indicate a regulatory change caused by reversible enzyme phosphorylation and dephosphorylation or sialization and desialization. Despite these differences, the sum of the two negatively charged residues was lower in tumour pyruvate kinase isoenzyme M2, with the slowest migration rate, than in normal rat liver isoenzyme M2. Moreover, isoenzyme M2 from tumour material, in comparison with isoenzyme M2 from normal rat liver, had a twice as high content of thiol groups (20 moles/mole protein), especially of free and superficially located ones, than the isoenzyme M2 from normal liver (10 moles/mole protein). This may explain abnormal susceptibility of tumour isoenzyme M2 to stereospecific inhibition by exogenous L-cysteine, and indicate genetically dependent changes in amino-acid content of tumour enzyme which take place during cell tumourigenic transformation.

Cutaneous leishmaniasis: iso-enzyme characterisation of Leishmania tropica

In order to identify and characterise the organisms responsible for Cutaneous Leishmaniasis, parasites were isolated from active lesions, grown in-vitro cultures and identified by iso-enzyme characterisation. Thirteen isolates from different patients were typed as L. tropica. Seven of these isolates were from Afghan refugees encamped in the suburbs of Islamabad, 3 were from patients in Multan, 1 was from a patient from Azad Jammu and Kashmir and 1 was from Besham (Swat, NWFP). The study confirms the presence of anthroponotic Cutaneous Leishamaniasis caused by L. Tropica in Pakistan.

Quantification of tumor type M2 pyruvate kinase (Tu M2-PK) in human carcinomas

Proliferating and tumor cells express a certain isoenzyme of pyruvate kinase, called PK type M2. This isoenzyme can be isolated in an active tetrameric and an inactive dimeric form. We have termed this form tumor type M2-PK. This tumor type pyruvate kinase can be quantified by a specific ELISA in blood sera and tumor homogenates. In this study we have compared 26 normal colon mucosa and colon cancer specimens from the same patients. The total specific pyruvate kinase activity and the amount of the tumour type M2-PK measured by ELISA was increased in the tumor samples compared to the normal colon mucosa of the same patient. In normal colon mucosa the specific PK-activity ranged between 0.21 and 1.25 U/mg protein whereas in colon carcinoma we found activities between 0.99 and 7.08 U/mg. The amount of tumor M2-PK measured by ELISA ranged between 0.82 and 27.10 U/mg protein in normal colon mucosa and between 1.96 and 242.40 U/mg protein in colon carcinoma. The tumor M2-PK content in the serum of 666 healthy blood donors was measured by ELISA and compared to sera from 15 colon carcinoma patients and showed a highly significant difference (Mann-Whitney rank sum test, p < 0.001). The values for the 50%-percentiles (median) of blood donors were 10.8 U/ml and 55.0 U/ml for colon carcinoma.

Induction of heat shock proteins DnaK, GroEL, and GroES by salt stress in Lactococcus lactis

The bacterium Lactococcus lactis has become a model organism in studies of growth physiology and membrane transport, as a result of its simple fermentative metabolism. It is also used as a model for studying the importance of specific genes and functions during life in excess nutrients, by comparison of prototrophic wild-type strains and auxotrophic domesticated (dairy) strains. In a study of the capacity of domesticated strains to perform directed responses toward various stress conditions, we have analyzed the heat and salt stress response in the established L. lactis subsp. cremoris laboratory strain MG1363, which was originally derived from a dairy strain. After two-dimensional separation of proteins, the DnaK, GroEL, and GroES heat shock proteins, the HrcA (Orf1) heat shock repressor, and the glycolytic enzymes pyruvate kinase, glyceral-dehyde-3-phosphate dehydrogenase, and phosphoglycerate kinase were identified by a combination of Western blotting and direct N-terminal amino acid sequencing of proteins from the gels. Of 400 to 500 visible proteins, 17 were induced more than twofold during heat stress. Two classes of heat stress proteins were identified from their temporal induction pattern. The fast-induced proteins (including DnaK) showed an abruptly increased rate of synthesis during the first 10 min, declining to intermediate levels after 15 min. GroEL and GroES, which also belong to this group, maintained a high rate of synthesis after 15 min. The class of slowly induced proteins exhibited a gradual increase in the rate of synthesis after the onset of stress. Unlike other organisms, all salt stress-induced proteins in L. lactis were also subjected to heat stress induction. DnaK, GroEL, and GroES showed similar temporal patterns of induction during salt stress, resembling the timing during heat stress although at a lower induction level. These data indicate an overlap between the heat shock and salt stress responses in L. lactis.

Changes in glucose transport activities in mammary adenocarcinoma of dogs

The activities of D-glucose transport (D-GT) and cytosolic enzymes were significantly higher in mammary adenocarcinoma of dogs than in mammary gland from normal dogs. The activities of D-GT in adenocarcinoma were over three-and-a-half times higher than in the controls. The K(m) value of the D-GT activity for glucose in both the adenocarcinoma and normal mammary gland was approximately 0.9 mM. The activities of the key glycolytic enzymes, hexokinase and pyruvate kinase, in the adenocarcinoma were also more than three-and-a-half times higher than in the controls. The increased activities of D-GT are considered to be accompanied by an acceleration of glucose utilisation in the adenocarcinoma of dogs.

Glycolytic enzyme binding during entrance to daily torpor in deer mice (Peromyscus maniculatus)

Associations of glycolytic enzymes with the subcellular particulate fraction of skeletal muscle and heart were examined during entrance to daily torpor in deer mice (Peromyscus maniculatus). In skeletal muscle a significant decrease in enzyme binding occurred during torpor entrance for phosphofructokinase, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate kinase, with an additional significant decrease for phosphofructokinase and pyruvate kinase during the deepest state of torpor. Reductions in enzyme binding during torpor entrance also occurred in heart; significant changes were observed in hexokinase, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate kinase binding. Contrary to the finding of additional reductions in enzyme binding seen in skeletal muscle, significant increases in enzyme binding during the deepest torpor state were observed for hexokinase, phosphofructokinase, glyceraldehyde-3-phosphate dehydrogenase, pyruvate kinase, and lactate dehydrogenase in heart. These results suggest that a decrease in the binding of glycolytic enzymes to subcellular structures in skeletal muscle and heart may be at least partially responsible for initiating the reduction in metabolic rate during torpor entrance. This decreased binding may continue to mediate the metabolic reduction in skeletal muscle throughout torpor; heart, however, may require the use of different molecular mechanisms. The increased binding in heart during the deepest state of torpor may represent an anticipatory response in preparation for increased activity during arousal.