Human Heart Fatty Acid-binding Protein Research Articles

Identification of B Cell Epitopes of Blo t 13 Allergen and Cross-Reactivity with Human Adipocytes and Heart Fatty Acid Binding Proteins.

Cross-reactivity between allergens and human proteins could have a clinical impact in allergic diseases. Blo t 13 is an allergen from the mite Blomia tropicalis, which belongs to the fatty acid binding protein (FABP) family and has structural homology with human FABPs. This work aimed to map B cell epitopes on Blo t 13 and to identify epitopes involved in cross-reactivity with human heart FABP (FABP3) and adipocyte FABP (FABP4). Sera from 25 patients with house dust mite (HDM) allergy that were sensitized to Blo t 13 were used for testing the reactivity of immunoglobulin E (IgE) and IgG to FABP. The epitope mapping of Blo t 13 was performed using overlapping peptides, and cross-reactivity between Blo t 13 and human FABP was analyzed using human sera and anti-Blo t 13 monoclonal antibodies. IgE antibodies to all FABPs were detected in 14/25 serum samples, and IgG was detected in 25/25 serum samples. The cross-reactivity of Blo t 13 was 42% with FABP3 and 48% with FABP4. Two IgE-binding regions were identified in Blo t 13; one between residues 54 and 72 (the main cross-reacting region) and another between residues 111 to 129. Our results suggest that exposure to the Blo t 13 allergen could induce an auto-reactive response to endogenous FABP in allergic patients sensitized to Blo t 13.

Effect of dexmedetomidine on myocardial injury marker and postoperative recognition during cardiac surgery

Objective To observe the effect of dexmedetomidine (DEX) on myocardial injury marker and postoperative recognition during cardiac surgery. Methods Fifty patients diagnosed with rheumatic heart disease were randomly divided into experiment group and control group. The experiment group was treated by DEX, and the control group was treated by normal saline. The removal time, intensive care unit (ICU) retention time, resuscitation after opening aortic, vital signs, changes of myocardial injury markers, and incidence of postoperative recognition were compared. Results There was no significant difference in the removal time, ICU retention time, and resuscitation after opening aortic between the two groups (P>0.05). The levels of systolic blood pressure (SBP) in the experiment group [(97.26±11.18), (106.93±11.75), and (104.35±11.09) mmHg (1 mmHg=0.133 kPa)] were higher than in the control group [(83.17±10.69), (95.16±13.33), and (97.03±7.08) mmHg] from period of cardiopulmonary bypass to the end of surgery (P<0.05); The levels of diastolic blood pressure (DBP) in the experiment group [(70.06±11.43), (60.44±9.47), (61.40±8.66), and (63.63±7.61) mmHg] after injection of loading dose, longitudinal sternotomy, the period from cardiopulmonary bypass to the end of surgery were higher than in the control group [(57.22±12.43), (56.45±9.06), (55.23±6.59), and (56.62±6.88) mmHg, P<0.05]; The levels of heart rate (HR) in the experiment group [(66.37±9.59), and (68.62±10.08)/min] after the incision, and longitudinal sternotomy were lower than in the control group [(75.52±12.08), and (81.64±8.79)/min, P<0.05]. The levels of 24-h human heart fatty acid binding protein (H-FABP) in the experiment group [(0.49±0.09), (1.74±0.13), (1.97±0.11), and (1.41±0.13) μg/ml] were lower than those in the control group [(0.58±0.14), (1.97±0.26), (2.35±0.41), and (1.57±0.21) μg/ml] after completion of cardiopulmonary bypass to the end of surgery (P<0.05); The levels of 24-h Creatine kinase isoenzyme MB(CK-MB) in the experiment group [(89.69±15.88) U/ml] were lower than in the control group [(116.85±18.27) U/ml, P<0.05]; The levels of 24-h cardiac Troponin Ⅰ (cTnⅠ) in the experiment group [(1.43±0.18), and (1.20±0.21) ng/ml] were lower than in the control group [(1.79±0.21), and (1.47±0.14) ng/ml, P<0.05]; The scores of mini-mental state examination (MMSE) and Montreal cognitive assessment scale (MoCA) in the experiment group [(28.23±1.52)/min, and (24.25±1.35)/min] were higher than those in the control group [(26.22±1.43)/min, and (22.03±1.51)/min, P<0.05]. Conclusion It can be concluded that DEX may reduce the myocardial injury and improve the condition of postoperative recognition. It could better maintain the hemodynamic stability during cardiac surgery. Key words: Cardiac surgery; Dexmedetomidine; Myocardial injury marker; Cognitive function

Carperitide and Atrial Fibrillation After Coronary Bypass Grafting

Background— Occurrence of atrial fibrillation after cardiac surgery is associated with long-term mortality. We investigated whether infusion of human atrial natriuretic peptide (carperitide) could prevent postoperative atrial fibrillation. Methods and Results— A total of 668 patients who underwent isolated coronary artery bypass grafting were randomized to receive infusion of carperitide or physiological saline from the initiation of cardiopulmonary bypass. Patients were monitored continuously for 1 week after surgery to detect atrial fibrillation. The risk factors were investigated by Cox proportional hazard model. Postoperative atrial fibrillation occurred in 41 of 335 patients (12.2%) from the carperitide group versus 110 of 333 patients (32.7%) from the placebo group ( P &lt;0.0001). Postoperative levels of angiotensin-II, aldosterone, creatine kinase MB isoenzyme, human heart fatty acid–binding protein, and brain natriuretic peptide were all significantly lower in the carperitide group. The risk factors for postoperative atrial fibrillation by the Cox proportional hazard model were an age ≥70 years, emergency surgery, preoperative aldosterone level &gt;150 ng/mL, preoperative nonuse of angiotensin receptor antagonists, preoperative use of calcium antagonists, postoperative nonuse of β-blockers, postoperative nonuse of aldosterone blockers, and nonuse of carperitide. Conclusions — Perioperative carperitide infusion reduced the occurrence of postoperative atrial fibrillation. Accordingly, carperitide could be a useful option for preventing postoperative atrial fibrillation. Clinical Trial Registration — URL: http://www.umin.ac.jp . Unique Identifier: UMIN000003958.

A Sensitive capacitive immunosensor for direct detection of human heart fatty acid-binding protein (h-FABP)

The fabrication of a capacitive interdigitated immunosensor (CID) based on a mixed self-assembled monolayer (mSAM) film for the direct detection of heart fatty-acid binding protein (h-FABP) without any labeling is described. The capacitance changes of mSAMs vs. homogenous ordered self-assembled monolayers (hSAMs) on gold work electrodes/covalently bonded antibodies/buffered medium are utilized for monitoring the specific antibody–antigen interaction. Capacitance measurements in the absence and presence of Faradaic currents were performed. The electrochemical properties of mixed monolayers were compared with those of a pure monolayer of 11-mercaptoundecanoic acid (MUA) self-assembled on gold surfaces. Taking into account the stability of the studied monolayers during the electrochemical experiments with the Faradaic process, the best SAM functionalization method was used for developing a sensitive capacitive immunosensor with a non-Faradaic process for direct immune detection of human h-FABP. Under the optimized conditions, the proposed mixed self-assembled monolayer (mSAM1) on gold electrode exhibited good insulating properties such as a capacitive behavior when detecting h-FABP from human serum in the range of 98pgml−1–100ngml−1, with a detection limit of 0.836ngml−1 comparative with a homogenous self-assembled monolayer (hSAM).

Quartz crystal microbalance for the cardiac markers/antibodies binding kinetic measurements in the plasma samples

The quartz crystal microbalance (QCM) was exploited for cardiac markers detection and kinetic studies of immunochemical reaction of cardiac troponin I (cTnI) and human heart fatty acid binding protein (H-FABP) with the corresponding monoclonal antibodies in undiluted plasma (serum) and standard solutions. The QCM technique allowed to dynamically monitor the kinetic differences in specific interactions and nonspecific sorption, without multiple labeling procedures and separation steps. The affinity binding process was characterized by the association (ka) and the dissociation (kd) kinetic constants and the equilibrium association (K) constant, all of which were obtained from experimental data.

Soluble ST2 and N-terminal pro-Brain Natriuretic Peptide Combination

Some potential biomarkers have been reported recently in patients with pulmonary arterial hypertension (PAH), but the most clinically useful among these potential biomarkers, especially in childhood PAH, has not been identified. Therefore, this study investigated which biomarker is useful in assessing severity of and patient prognosis in childhood idiopathic PAH (IPAH)/heritable PAH (HPAH). Fifty-nine patients who were younger than 16 years at onset of IPAH/HPAH were selected. The following 10 biomarker candidates were quantified: high-sensitivity troponin T, human heart fatty acid-binding protein, N-terminal pro-brain natriuretic peptide (NT-proBNP), pentraxin-3, soluble ST2 (sST2), angiopoietin-2 (Ang-2), matrix metalloproteinase 2, tenascin C, endostatin (ES), and thymidine kinase. Functional characteristics and clinical outcomes were analyzed retrospectively. NT-proBNP, sST2, Ang-2, and ES correlated well with New York Heart Association class. On area under the receiver operating characteristic curve analysis, sST2 had a significantly good relationship with prognosis. On Kaplan-Meier curve and univariate Cox regression analyses, elevated sST2 and NT-proBNP level predicted poor outcome of the present patients with childhood IPAH/HPAH. Furthermore, patients with elevated sST2 had significantly worse prognosis among those with high NT-proBNP. The sST2 and NT-proBNP combination is a useful biomarker to predict clinical condition and outcome in patients with childhood IPAH/HPAH.

Feasibility of landiolol and bisoprolol for prevention of atrial fibrillation after coronary artery bypass grafting: A pilot study

We previously performed a trial of intravenous landiolol hydrochloride during and after cardiac surgery (the PASCAL trial) and demonstrated a preventive effect on postoperative atrial fibrillation (AF). In the present study, we investigated the efficacy of increasing the dose and administration period of landiolol for prevention of postoperative AF, as well as the effect of oral bisoprolol in the early postoperative period. A total of 105 patients who underwent coronary artery bypass grafting were randomized to 3 groups: a group receiving intravenous landiolol perioperatively at 5 μg/kg/min for 3 days (group L), a group receiving oral bisoprolol postoperatively together with landiolol (group LB), and a control group without beta-blocker therapy (group C). The primary end point was the presence/absence of postoperative AF. Secondary end points were (1) the early clinical outcome, (2) hemodynamics, (3) cardiac enzymes (creatine kinase isoenzyme MB, troponin-I, and human heart fatty acid-binding protein), (4) high-sensitivity C-reactive protein (hs-CRP) and pentraxin-3, (5) asymmetric dimethylarginine (ADMA), and (6) brain natriuretic peptide. Postoperative AF occurred in 14.5% of group L, 9.1% of group LB, and 35.3% of group C. A significant difference was observed between groups LB and C. Significantly higher levels of troponin-I, human heart fatty acid-binding protein, hs-CRP, pentraxin-3, and ADMA were noted in group C than in groups L and LB. Landiolol and bisoprolol prevented postoperative AF. The anti-ischemic, anti-inflammatory, and anti-oxidant effects of these beta-blockers presumably inhibited the onset of AF.

Myocardial Protective Effect of Human Atrial Natriuretic Peptide in Cardiac Surgery - "hANP Shot" in Clinical Safety Trial -

We studied low-dose human atrial natriuretic peptide (hANP) infusion therapy during cardiac surgery and reported the cardiac and renal protective effects. The efficacy of a bolus injection of hANP (the "hANP shot") simultaneously with induction of cardioplegia has been proven in animal experiments. In the present study the clinical effects of this "hANP shot" were examined. The subjects were 67 patients undergoing Coronary artery bypass grafting. At the time of inducing cardioplegia, 1 group received a simultaneous bolus injection of 100 μg of hANP (hANP group) and the other group received an injection of physiological saline (placebo group). The primary endpoints were (1) operative mortality and complications, and (2) the creatine kinase isoenzyme MB (CPK-MB), troponin-I, and human heart fatty acid binding protein (H-FABP) levels. The secondary endpoints were (1) the incidence of arrhythmia, and levels of (2) atrial and B-type natriuretic peptides, and cyclic guanosine monophosphate (cGMP), and (3) renin, angiotensin II, and aldosterone. Postoperative CPK-MB, troponin-I, and H-FABP levels were significantly lower in the hANP group than in the placebo group. Postoperative arrhythmia was significantly less frequent in the hANP group than in the placebo group. It is possible to achieve cardioprotective effects based on the safety of the "hANP shot", as well as from biomarkers of ischemia and results related to arrhythmia. The "hANP shot" should also be evaluated as a safer and new cardioprotective method for cardiac surgery.

Effects of autotransfusion of mediastinal shed blood on biochemical markers of myocardial damage in coronary surgery

Previous studies have shown conflicting results regarding the effect of autotransfusion of mediastinal shed blood after coronary artery bypass grafting (CABG) on the serum levels of myocardial band (MB) isoenzymes of creatine kinase (CK-MB) and cardiac troponins. The effect of autotransfusion on serum levels of human heart fatty acid binding protein (H-FABP), another marker of myocardial necrosis, has not been studied. The aim of the present study was to investigate the effects of autotransfusion of mediastinal shed blood on the serum levels of CK-MB, cardiac troponin T (cTnT), and H-FABP after uncomplicated primary CABG. Fifty patients were randomized to post-operative autotransfusion of mediastinal shed blood or no autotransfusion. Blood samples for the analysis of the biochemical markers of myocardial damage were drawn pre-operatively and 1, 4, 12, 24, 48, and 72 h after the termination of cardiopulmonary bypass. Samples from the mediastinal shed blood were collected after 1 and 4 h. The levels of the biochemical markers of myocardial injury were all markedly elevated in mediastinal shed blood. Autotransfusion did not significantly affect the serum levels of cTnT or H-FABP. However, during the early post-operative hours, there was a trend towards a higher level of cTnT and H-FABP in the autotransfusion group. During the first 24 h after surgery, the autotransfusion group had a significantly higher serum level of CK-MB. Post-operative autotransfusion of mediastinal shed blood may contribute to elevated serum levels of biochemical markers of myocardial injury.

Leukocyte-depleted terminal blood cardioplegia provides superior myocardial protective effects in association with myocardium-derived nitric oxide and peroxynitrite production for patients undergoing prolonged aortic crossclamping for more than 120 minutes

Objectives This study was designed to examine the myocardial protective effect of leukocyte-depleted terminal blood cardioplegia in association with nitric oxide and peroxynitrite production, especially for patients undergoing prolonged aortic crossclamping. Methods Fifty-four patients (34 men, 20 women, mean age 56.7 ± 12.7 years) undergoing aortic valve replacement were randomly allocated to one of two groups; group LDTC (n = 27) received 10 minutes of leukocyte-depleted terminal blood cardioplegic solution, and group CONT (n = 27) served as controls. Each group was subdivided into 2 groups: aortic crossclamping for less than 120 minutes in groups LDTC-S (n = 13) and CONT-S (n = 14); aortic crossclamping for 120 minutes or more in groups LDTC-L (n = 14) and CONT-L (n = 13). Results After aortic unclamping, group LDTC-L showed higher incidence of spontaneous defibrillation (78.6% vs 30.8%, P = .0213), higher plasma nitrate + nitrite in the coronary sinus effluent (32.5 ± 4.1 vs 28.7 ± 3.0 μmol/L, P = .0013), lower differences between coronary sinus effluent and arterial blood in the percentage ratio of nitrotyrosine to tyrosine (myocardium-derived peroxynitrite; 2.987% ± 0.576% vs 3.951% ± 0.952%, P = .0036), and plasma polymorphonuclear-elastase (113.9 ± 21.3 vs 155.5 ± 41.6 μg/L, P = .0029) and malondialdehyde (2.75 ± 0.67 vs 4.02 ± 0.96 μmol/L, P = .0005) than group CONT did. Postoperatively, group LDTC-L showed lower human-heart fatty acid–binding protein (111.4 ± 25.2 vs 156.4 ± 38.6 IU/L, P = .0013), lower creatine kinase–muscle and brain (19.2 ± 4.7 vs 24.8 ± 6.5 IU/L, P = .0120), and smaller requirement of catecholamine (5.44 ± 2.29 vs 8.45 ± 3.42 μg · kg −1 · min −1, P = .0122). There were no significant differences in these parameters between groups LDTC-S and CONT-S. Conclusions This study demonstrated that leukocyte-depleted terminal blood cardioplegia provided superior myocardial protective effects and regulated myocardial-derived nitric oxide and peroxynitrite production only for patients undergoing aortic crossclamping for more than 120 minutes. The results suggest that prolonged aortic crossclamping deteriorates the tolerance to leukocyte-mediated myocardial injury accompanied by endothelial dysfunction associated with nitric oxide and peroxynitrite production.

Development of a disposable immunosensor for the detection of human heart fatty-acid binding protein in human whole blood using screen-printed carbon electrodes

An amperometric immunosensor for the rapid detection of human heart fatty-acid binding protein (H-FABP) in whole blood was developed. Due to its rapid kinetics in plasma, H-FABP is a useful biochemical marker for the early assessment of acute myocardial infarction (AMI). A one-step direct sandwich assay in which analyte and alkaline phosphatase (AP) labelled antibody were simultaneously added to the immobilised primary antibody, was employed using two distinct monoclonal mouse anti-human H-FABP antibodies. p-Aminophenyl phosphate was converted to p-aminophenol by AP and the current generated by its subsequent oxidation at +300 mV vs. Ag/AgCl was measured. Total assay time was 50 min and the standard curve was linear between 4 and 250 ng ml −1. The intra- and inter-assay coefficients of variation were below 9%. No cross-reactivity of the antibodies was found with other early cardiac markers and endogenous substances in whole blood did not have an interfering effect. The overall performance of the sensor, wide working range, good precision and specificity demonstrate its potential usefulness for early assessment of AMI.

A genetically engineered fusion protein with horseradish peroxidase as a marker enzyme for use in competitive immunoassays.

Horseradish peroxidase is one of the most widely used marker enzymes in immunoassays. Several disadvantages are encountered upon chemical conjugation of peroxidase with antibodies or antigens, as are low reproducibility and undefined stoichiometry. We here describe for the first time the production of a recombinant fusion of a protein analyte with horseradish peroxidase in Escherichia coli, employing refolding of inclusion bodies and reconstitution with heme. The genetic fusion approach enables preparation of conjugates with 1:1 stoichiometry and defined structure. As a protein analyte, the human heart fatty acid binding protein (H-FABP) was chosen, which is a new and sensitive marker for acute myocardial infarction. The recombinant conjugate was fully active [650 U/mg with 2,2-azino-bis(3-ethyl-thiazoline-6-sulfonate) as substrate] and obtained in a yield of 12 mg/L of E. coli culture, which is better than that for recombinant peroxidase alone. The competitive immunoassay that was developed with the recombinant conjugate requires fewer incubation steps than the traditional sandwich ELISA format. It permitted the detection of H-FABP directly in plasma in the range of 10-1500 ng/mL which is the relevant range for clinical decision-making.

Clinical evaluation of leukocyte-depleted blood cardioplegia for pediatric open heart operation

Background. Blood cardioplegia (BCP) is widely used for myocardial protection during open heart operation. However, BCP may have a chance to induce neutrophil-mediated myocardial injury during aortic cross-clamping. We clinically evaluated the myocardial protective effect of leukocyte-depleted blood cardioplegia (LDBCP) for initial and intermittent BCP administration in pediatric patients. Methods. Fifty patients undergoing open heart operation for congenital heart disease between January 1997 and March 1999 were reviewed. Twenty-five were administered LDBCP for myocardial protection during ischemic periods (LDBCP group), and the remaining 25 were given BCP without leukocyte depletion (BCP group). Results. The difference in plasma concentrations of malondialdehyde between coronary sinus effluent blood and arterial blood just after reperfusion in the LDBCP group (1.68 ± 0.56 μmol/L) was significantly lower than that in the BCP group (2.35 ± 0.62 μmol/L; p < 0.01). The LDBCP group showed significantly lower plasma concentrations of human heart fatty acid-binding protein at 50 minutes after reperfusion (LDBCP group, 103.5 ± 38.7 IU/L; BCP group, 144.8 ± 48.8 IU/L; p < 0.01) and the peak value of creatine kinase-MB during the first 24 postoperative hours (LDBCP group, 17.0 ± 8.5 IU/L; BCP group, 26.0 ± 11.6 IU/L; p < 0.01) than did the BCP group. The maximum dose of catecholamine was significantly smaller in the LDBCP group (LDBCP group, 3.20 ± 2.18 μg · kg −1 · min −1; BCP group, 5.60 ± 2.83 μg · kg −1· min −1; p < 0.01). Conclusions. These results suggest the usefulness of LDBCP for protection from the myocardial injury that can be induced by BCP administration during aortic cross-clamping.

Functional and conformational characterization of new mutants of heart fatty acid-binding protein

In this study we investigated the possible involvement of several amino acids (not located in the ligand-binding centre) in fatty acid binding and conformational stability of heart fatty acid-binding protein (H-FABP). We prepared recombinant human H-FABP proteins with mutations in the hydrophobic patch (Phe4, Trp8 and Phe64), portal region (Phe16), hinge region (Leu66, Gly67), second portal region (Glu72) and at the protein surface (Lys21) respectively. Oleic acid-binding affinity and conformational stability of human H-FABP are significantly decreased or completely lost by mutation of Trp8 or Phe16. NMR spectra confirmed that these residues are important for the stability of the protein fold. Substitution of Phe4 or Phe64 resulted in less stability, but oleic acid-binding affinity was not affected. Mutation of Lys21 had no effect on either structural integrity or fatty acid-binding affinity. Replacement of Leu66 or Gly67 did not affect fatty acid binding, but protein stability was reduced. Finally, mutation of Glu72 to Ser caused no change of affinity, but NMR spectra and urea-denaturation curves showed the extremely poor stability of this mutant. In conclusion, no relationship was observed between fatty acid-binding affinity and conformational stability.

Functional and conformational characterization of new mutants of heart fatty acid-binding protein

In this study we investigated the possible involvement of several amino acids (not located in the ligand-binding centre) in fatty acid binding and conformational stability of heart fatty acid-binding protein (H-FABP). We prepared recombinant human H-FABP proteins with mutations in the hydrophobic patch (Phe(4), Trp(8) and Phe(64)), portal region (Phe(16)), hinge region (Leu(66), Gly(67)), second portal region (Glu(72)) and at the protein surface (Lys(21)) respectively. Oleic acid-binding affinity and conformational stability of human H-FABP are significantly decreased or completely lost by mutation of Trp(8) or Phe(16). NMR spectra confirmed that these residues are important for the stability of the protein fold. Substitution of Phe(4) or Phe(64) resulted in less stability, but oleic acid-binding affinity was not affected. Mutation of Lys(21) had no effect on either structural integrity or fatty acid-binding affinity. Replacement of Leu(66) or Gly(67) did not affect fatty acid binding, but protein stability was reduced. Finally, mutation of Glu(72) to Ser caused no change of affinity, but NMR spectra and urea-denaturation curves showed the extremely poor stability of this mutant. In conclusion, no relationship was observed between fatty acid-binding affinity and conformational stability.

Early Detection of Cardiac Damage With Heart Fatty Acid-Binding Protein After Cardiac Operations

Background. It is still difficult to evaluate myocardial damage in the acute phase of reperfusion in cardiac operations. We investigated the clinical significance of human heart fatty acid-binding protein (HH-FABP) for detecting myocardial damage after cardiac operations earlier than creatine kinase MB isoform or troponin-T. Methods. Blood samples from 20 patients who underwent coronary artery bypass grafting were collected serially after reperfusion to measure serum levels of creatine kinase-MB, troponin-T, and HH-FABP. Results. Serum HH-FABP levels peaked earliest after reperfusion. In addition, the maximum serum HH-FABP level was predictable immediately after reperfusion. The maximum serum HH-FABP level correlated with the maximum serum creatine kinase-MB or troponin-T level, as well as with the aortic cross-clamp time or the maximum dose of catecholamines administered after reperfusion. Conclusions. Measurements of HH-FABP allow for earlier evaluation of myocardial damage in the acute phase of reperfusion. Human heart fatty acid-binding protein may be a useful indicator of myocardial damage after cardiac operations.

Identification of a human heart FABP pseudogene located on chromosome 13

The fatty acid-binding proteins (FABPs) constitute a conserved group of cytosolic low molecular mass proteins, which consists of several types: liver, heart, myelin, epidermal, adipocyte, brain, intestinal and ileal type. The FABP gene structure is well conserved during evolution and exhibits a four-exon/three-intron structure. In the past, multiple hybridizing fragments were detected upon Southern blot analysis using heart FABP (H-FABP) cDNA as a probe. The origin of these fragments was not clear. We screened a human genomic library and isolated an intronless gene ( FABP3-ps) with 85% similarity to the human H-FABP cDNA and high similarity (76 and 79%) to the H-FABP cDNAs of mouse and bovine, respectively. By means of fluorescence in situ hybridization this processed pseudogene could be assigned chromosome 13q13-q14, whereas the gene for human H-FABP ( FABP3) resides on chromosome 1p32-p33. No expression of the processed pseudogene could be detected in skeletal muscle or fetal brain.

Purification and structural characterization of a fatty acid-binding protein from the liver of the catfish Rhamdia sapo

We report here the isolation of a fatty acid-binding protein (FABP) from the liver of the catfish Rhamdia sapo. The purification procedure involves gel filtration, anion-exchange chromatography and reverse-phase high-performance liquid chromatography. The purified protein is basic (pI > 8.7) and migrates on sodium dodecyl sulfate-gel electrophoresis as a single entity of about 15 kDa. Its amino acid composition resembles those of FABPs isolated from other animals. Unlike mammalian liver FABPs, catfish liver FABP contains at least one tryptophan residue per molecule. No significant cross-reactivity was observed between the purified protein and polyclonal antibodies against either rat liver FABP or rat heart FABP. Amino acid sequencing of peptides obtained by digestion with Lys-C revealed that the catfish protein is structurally more similar to chicken liver FABP (69% identity in a 67-residue overlap) than to human liver FABPs (36%), nurse shark ( Ginglymostoma cirratum) liver FABP (30%) and human heart FABP (31%). Taken together, these results suggest that catfish liver FABP is far more closely related to chicken liver FABP than to the FABPs isolated from the liver of mammals or elasmobranchs.

Enzyme immunosensor for diagnosis of myocardial infarction

Amperometric enzyme immunosensors have been developed for the detection of the early myocardial infarction marker heart fatty acid binding protein (H-FABP) in blood plasma. They are based on anti-H-FABP antibodies immobilized on nitrocellulose or activated nylon membranes covering a modified Clark-type oxygen electrode. Two approaches have been tested using bovine H-FABP as a model: (i) the competition principle, where defined amounts of glucose oxidase (GOD)-labelled H-FABP compete with free H-FABP for binding to the immobilized capture antibodies; (ii) the sandwich principle, where the free H-FABP binds to the immobilized capture antibody and to a secondary GOD-labelled antibody, forming a sandwich. In both approaches, after addition of glucose, the activity of the enzyme label is determined with the amperometric electrode within minutes. The immunosensor using the sandwich principle on activated nylon membranes can be used repeatedly for at least 10 measurements after regeneration of the antibody membranes without loss of binding capacity of the capture antibodies. For the determination of human H-FABP, the sandwich principle with monoclonal anti-bovine-H-FABP antibodies as capture and GOD-labelled goat-anti-human-H-FABP antibodies as secondary antibodies is chosen. Initial experiments demonstrate that the sensitivity of the immunosensor is sufficient for the determination of clinical levels of H-FABP in plasma after myocardial infarction (100–300 ng ml −1).

Monoclonal antibodies to human heart fatty acid-binding protein

Heart-type fatty acid-binding protein (H-FABP), a 15 kDa non-enzymatic protein, which is abundantly present in heart and some skeletal muscles, was recently found to be a useful plasma marker for acute myocardial infarction. The BIAcore biosensor technology was used to raise and characterize a panel of 13 monoclonal antibodies against human H-FABP which did not crossreact with other FABP types of human origin. The kinetics of association and dissociation between FABP and the monoclonal antibodies was studied. By pairwise mapping several distinct epitopes could be identified.