Development of a protein assay with copper chelator chromeazurol B, based on the biuret reaction.

This study aimed to provide a novel and highly sensitive protein assay based on the biuret reaction and using chromeazurol B, a metal chelate compound. The method consists of two reagents and an automated analyzer. First, a complex of copper and protein (biuret reaction) is formed. Second, a chelating reagent containing chromeazurol B forms a three-dimensional complex of protein, copper, and chromeazurol B at neutral pH, resulting in highly sensitive coloration. The intra-assay (n = 20) variation for the three levels was 3.54 % or lower at each concentration. Each response with α, ß-, and γ-globulin was 103.8 % and 104.3 %, respectively, against albumin. The molar absorption coefficient (ε) of the present method was 2.5 × 105 m2/mol against human albumin, higher than that of the commercially available Lowry method (ε = 8.7 × 104 m2/mol), which is based on the same principle. The correlation test for the pyrogallol method with 30 urine samples showed good performance (r = 0.961). The method described here (the Biuret-based CAB method) is a more sensitive and rapid assay than the Lowry method, and it may also be applied to biological samples because of its similar reactivity towards various proteins.

Comparison of the Japan Society of Clinical Chemistry reference method and CDC method for HDL and LDL cholesterol measurements using fresh sera.

OBJECTIVES: In 2009, the Japan Society of Clinical Chemistry (JSCC) recommended a reference method for the measurement of serum high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) levels. This automated method uses cholesterol esterase-cholesterol dehydrogenase to measure cholesterol levels in fractions obtained after ultracentrifugation and dextran sulfate/magnesium chloride precipitation. In the present study, using fresh samples, we compared the LDL-C and HDL-C levels measured using this method with those measured using the traditional Centers for Disease Control and Prevention (CDC)-beta-quantification (BQ) method. DESIGN: and methods: Using both the JSCC and CDC-BQ methods, LDL-C/HDL-C levels were measured in 47 non-diseased and 126 diseased subjects, whose triglyceride levels were lower than 11.29 â€‹mmol/L (1000 â€‹mg/dL). RESULTS: For LDL-C, the equation of the line representing the correlation between the two methods was y â€‹= â€‹0.991x + 0.009 â€‹mmol/L; r â€‹= â€‹0.999; and Sy/x â€‹= â€‹0.025 â€‹mmol/L, where x is the mean LDL-C level measured using the CDC-BQ method. Similarly, for HDL-C, the equation of the line representing the correlation between the two methods was y â€‹= â€‹0.988x + 0.041 â€‹mmol/L, r â€‹= â€‹0.999, and Sy/x â€‹= â€‹0.019 â€‹mmol/L, where x is the mean HDL-C level measured using the CDC-BQ method. CONCLUSIONS: The JSCC method agreed with the CDC-BQ method in cases of both non-diseased and diseased subjects, including those with dyslipidemia.

New colorimetric method with bromocresol purple for estimating the redox state of human serum albumin.

Oxidative damage results in protein modification and is observed in many diseases, such as heart failure and renal insufficiency. Human serum albumin is an index of oxidative change and is conventionally measured using high-performance liquid chromatography (HPLC). Although this method is more sensitive than the colorimetric method, it is time-consuming for clinical practice and the sera must be stored at -80°C before analysis. To overcome these limitations, in the present study we developed a new reagent for a more rapid and convenient quantification of oxidative stress, involving determination of the ratio of human nonmercaptalbumin to total albumin using a colorimetric method with bromocresol purple. The clinical utility of the developed reagent was confirmed by demonstrating the consistently higher oxidative stress levels in dialysis patients than in healthy control subjects, matching the results of the conventional HPLC method. This novel approach could be a valuable tool for immediate estimation of the state of oxidative stress during the course of disease and treatment, and could aid clinical treatment decisions.

Protein C and protein S deficiencies may be related to survival among hemodialysis patients.

BACKGROUND: Thrombophilia due to protein C (PC) and protein S (PS) deficiencies is highly prevalent among patients with stage 5 chronic kidney disease and is reported to arise due to extracorporeal circulation during hemodialysis (HD). This study aimed to evaluate the relationship between HD treatment and thrombophilia. METHODS: A total of 114 Japanese patients on maintenance HD (62 men, 52 women) were followed during 2008-2011. Their survival rates were compared against the duration of HD. Prior to each HD, coagulation/fibrinolysis parameters and PC and PS activities were measured using standard techniques. The patients were divided into two groups: Group 1, with PC and/or PS deficiencies (n = 32), and Group 2, without PC and PS deficiencies (n = 82). The influence of such deficiencies and duration of dialysis on survival was examined. Time-to-event analysis was applied using Kaplan-Meier estimates, and the log-rank test was proposed to test the equivalence of relative survival data. Hazard ratios and 95% confidence intervals (CI) were calculated. RESULTS: Of the 114 patients, 37 died (Group 1, 22; Group 2, 15). The hazard ratio (95% CI) was higher (p = 0.004) in Group 1 than Group 2. Gene analyses of PC and PS were performed in 14 patients from Group 1. No mutations in either protein were observed. We analyzed the causes of death in both groups; however, the estimated thrombophilia-related incidence of death could not be determined due to small sample size of HD patients. CONCLUSIONS: Our results suggest that PC and PS deficiencies may be related to survival in HD patients. However, this finding warrants additional research.

Significance of a Family-based Study of Hereditary Thrombosis: A Single-family Case Series of Protein C Deficiency.

Thrombophilia is a serious unpredictable complication caused by gene mutations, resulting in anticoagulant deficiencies. We herein report a single-family case series of protein C (PC) deficiency. Case 1 involved a Japanese man whose PC deficiency resulted in severe systemic thrombosis. The patients in cases 2 and 3 were his daughters who were diagnosed with PC deficiency via carrier screening in 2001 and later both became pregnant. Owing to appropriate treatments during pregnancy, they did not develop thrombosis and safely gave birth to healthy infants. This family case series suggests that appropriate knowledge concerning thrombophilia helps prevent future emergencies.

The Influence of Pre-Analytical Factors on the Analysis of Circulating MicroRNA.

BACKGROUND: MicroRNAs (miRNA) are expected as useful biomarkers for various diseases. We studied the pre-analytical factors causing variation in the analysis of miRNA. MATERIAL AND METHODS: Blood samples were collected from 25 healthy subjects. Plasma and serum were obtained from the same samples. The levels of miR-451, -16, -126, and -223 were analyzed using RT-qPCR. Cel-miR-39 was added as a spiked-in control in each sample. RESULTS: With the exception of miR-451, the levels of the miRNAs in plasma were higher than in serum. After high-speed centrifugation, the levels of miRNAs were almost equal between plasma and serum except for miR-451. Membrane filtration with 0.45 µm pore size reduced the levels of plasma miRNAs. The coagulation accelerators for serum processing did not affect the analysis of miRNA. The use of fraction containing particles of > 0.45 µm in size showed the inhibitory effect on the analysis of plasma miR-451. The RNase inhibitor was effective for protecting against the degradation of miRNAs. CONCLUSION: Plasma contains factors modifying miRNA profiles. The immediate processing of plasma with membrane filtration and RNase inhibitor may be a relevant method for achieving the stable analysis of miRNA.

Novel enzymatic method for assaying Lp-PLA2 in serum.

BACKGROUND: Measurement of lipoprotein-associated phospholipase A2 (Lp-PLA2) can be used as an adjunct to traditional cardiovascular risk factors for identifying individuals at higher risk of cardiovascular events. This can be performed by quantification of the protein concentration using an ELISA platform or by measuring Lp-PLA2 activity using platelet-activating factor (PAF) analog as substrate. Here, an enzymatic Lp-PLA2 activity assay method using 1-O-Hexadecyl-2-acetyl-rac-glycero-3-phosphocholine (rac C16 PAF) was developed. METHODS: The newly revealed substrate specificity of lysoplasmalogen-specific phospholipase D (lysophospholipase D (LysoPLD)) was exploited. Lp-PLA2 hydrolyzes 1-O-Hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (C16 PAF) to 1-O-Hexadecyl-2-hydroxy-sn-glycero-3-phosphocholine (LysoPAF). LysoPLD acted on LysoPAF, and the hydrolytically released choline was detected by choline oxidase. RESULTS: Regression analysis of Lp-PLA2 activity measured by the enzymatic Lp-PLA2 activity assay vs. two chemical Lp-PLA2 activity assays, i.e. LpPLA2 FS and PLAC® test, and ELISA, gave the following correlation coefficients: 0.990, 0.893 and 0.785, respectively (n = 30). CONCLUSION: Advantages of this enzymatic Lp-PLA2 activity assay compared with chemical Lp-PLA2 methods include the following; (i) only requires two reagents enabling a simple two-point linear calibration method with one calibrator (ii) no need for inhibitors of esterase-like activity in serum.

Characterization and application of a novel nicotinamide mononucleotide adenylyltransferase from Thermus thermophilus HB8.

Herein, we describe a novel enzymatic cycling method to measure nicotinamide mononucleotide (NMN) or nicotinic acid mononucleotide (NaMN), which are precursors of NAD biosynthesis. A gene encoding an NMN adenylyltransferase (NMNAT, EC 2.7.7.1) homologue was identified in Thermus thermophilus HB8. The gene from T. thermophilus (TtNMNAT) was engineered for expression in Escherichia coli and the recombinant enzyme found to be stable, retaining full activity after incubation for 45 min at 70°C. The Km values for NMN and ATP were calculated to be 0.263 and 1.27 mM, respectively, with a Vmax value of 60.3 µmoL/min/mg. TtNMNAT was successfully applied to the colorimetric NMN or NaMN assays, which employed (i) adenylation of NMN to NAD by TtNMNAT or adenylation of NaMN to deamido-NAD (NaAD) by TtNMNAT followed by amidation of NaAD to NAD by NAD synthetase (NADS, EC 6.3.1.5) and (ii) an NAD cycling reaction using 12α-hydroxysteroid dehydrogenase (12α-HSD, EC 1.1.1.176) and diaphorase (DI, EC 1.6.99.3) to accumulate reduced WST-8. This enzymatic cycling method enabled detection of 0.5 µM (12.2 nM in the reaction mixture) NMN or NaMN in an automatic clinical analyzer.

Highly sensitive reversed-phase high-performance liquid chromatography assay for the detection of Tamm-Horsfall protein in human urine.

BACKGROUND: Tamm-Horsfall protein (also known as uromodulin) is the most abundant urinary protein in healthy individuals. Since initially characterized by Tamm and Horsfall, the amount of urinary excretion and structural mutations of Tamm-Horsfall protein is associated with kidney diseases. However, currently available assays for Tamm-Horsfall protein, which are mainly enzyme-linked immunosorbent assay-based, suffer from poor reproducibility and might give false negative results. METHODS: We developed a novel, quantitative assay for Tamm-Horsfall protein using reversed-phase high-performance liquid chromatography. A precipitation pretreatment avoided urine matrix interference and excessive sample dilution. High-performance liquid chromatography optimization based on polarity allowed excellent separation of Tamm-Horsfall protein from other major urine components. RESULTS: Our method exhibited high precision (based on the relative standard deviations of intraday [≤2.77%] and interday [≤5.35%] repetitions). The Tamm-Horsfall protein recovery rate was 100.0-104.2%. The mean Tamm-Horsfall protein concentration in 25 healthy individuals was 31.6 ± 18.8 mg/g creatinine. There was a strong correlation between data obtained by high-performance liquid chromatography and enzyme-linked immunosorbent assay (r = 0.906), but enzyme-linked immunosorbent assay values tended to be lower than high-performance liquid chromatography values at low Tamm-Horsfall protein concentrations. CONCLUSIONS: The high sensitivity and reproducibility of our Tamm-Horsfall protein assay will reduce the number of false negative results of the sample compared with enzyme-linked immunosorbent assay. Moreover, our method is superior to other high-performance liquid chromatography methods, and a simple protocol will facilitate further research on the physiological role of Tamm-Horsfall protein.

Preliminary evaluation of an improved enzymatic assay method for measuring potassium concentrations in serum.

BACKGROUND: K(+) has important physiological functions. K(+) concentrations in serum are generally determined using ion-selective electrodes (ISEs), though measurement using reagents in aqueous medium is also useful. METHODS: K(+) concentrations were measured using recombinant inosine 5'-monophosphate dehydrogenase (IMPDH), which was activated only by K(+) and NH4(+). Exogenous NH4(+) and endogenous NH4(+) were eliminated using glutamine synthase. RESULTS: Regression analysis of the enzymatic assay (y) vs. the ISE method (x) gave the following relation: y=1.03x+0.09 (n=54, Sy,x=0.06 mmol/l). The linear range was up to 12 mmol/l when 1 U/ml IMPDH was used. CONCLUSION: Advantages of the proposed assay method are: (i) the measured range is wider than that of existing enzymatic methods; (ii) the conditions for K(+) determination can be maintained constant, regardless of the amount of NH4(+) in the analyte and reagents; and (iii) the elimination system is simpler because the recombinant IMPDH is stimulated by only K(+) and NH4(+) and is unaffected by biological materials.

Total cholesterol performance of Abell-Levy-Brodie-Kendall reference measurement procedure: Certification of Japanese in-vitro diagnostic assay manufacturers through CDC's Cholesterol Reference Method Laboratory Network.

BACKGROUND: Accurate measurement of total cholesterol (TC) is important for cardiovascular disease risk management. The US Centers for Disease Control and Prevention (CDC) and Cholesterol Reference Method Laboratory Network (CRMLN) perform Abell-Levy-Brodie-Kendall (AK) reference measurement procedure (RMP) for TC as a secondary reference method, and implement Certification Protocol for Manufacturers. Japanese CRMLN laboratory at Osaka performed the AK RMP for 22 years, and conducted TC certification for reagent/calibrator/instrument systems of six Japanese manufacturers every 2 years for 16 years. Osaka TC performance was examined and compared to CDC's reference values. METHODS: AK RMP involved sample hydrolysis, cholesterol extraction, and determination of cholesterol levels by spectrophotometry. The Certification Protocol for Manufacturers includes comparison with AK RMP using at least 40 fresh specimens. Demonstration of average bias ≤3% and total coefficient of variation ≤3% qualified an analytical system for certification. RESULTS: In the AK RMP used in the Osaka CRMLN laboratory, the regression equation for measuring TC was y (Osaka)=1.000x (CDC)+0.032 (n=619, R(2)=1.000). Six Japanese manufacturers had allowable performance for certification. CONCLUSIONS: The AK RMP for TC measurement was accurate, precise, and stable for 22 years. Six Japanese manufacturers were certified for 16 years.

HDL cholesterol performance using an ultracentrifugation reference measurement procedure and the designated comparison method.

BACKGROUND: Accurate high-density lipoprotein cholesterol (HDL-C) measurements are important for management of cardiovascular diseases. The US Centers for Disease Control and Prevention (CDC) and Cholesterol Reference Method Laboratory Network (CRMLN) perform ultracentrifugation (UC) reference measurement procedure (RMP) to value assign HDL-C. Japanese CRMLN laboratory (Osaka) concurrently runs UC procedure and the designated comparison method (DCM). Osaka performance of UC and DCM was examined and compared with CDC RMP. METHODS: CDC RMP involved UC, heparin-MnCl2 precipitation, and cholesterol analysis. CRMLN DCM for samples containing <200 mg/dl triglycerides involved 50-kDa dextran sulfate-MgCl2 precipitation and cholesterol determination. RESULTS: HDL-C regression equations obtained with CDC (x) and Osaka (y) were y=0.992x+0.542 (R(2)=0.996) for Osaka UC and y=1.004x-0.181 (R(2)=0.998) for DCM. Pass rates within ±1 mg/dl of the CDC target value were 91.9 and 92.1% for Osaka UC and DCM, respectively. Biases at 40 mg/dl HDL-C were +0.22 and -0.02 mg/dl for Osaka UC and DCM, respectively. CONCLUSIONS: Osaka UC and DCM were highly accurate, precise, and stable for many years, assisting manufacturers to calibrate products for clinical laboratories to accurately measure HDL-C for patients, calculate non-HDL-C, and estimate low-density lipoprotein cholesterol with the Friedewald equation.

LDL cholesterol performance of beta quantification reference measurement procedure.

BACKGROUND: Accurate measurement of blood lipids is crucial in cardiovascular disease risk management. The Centers for Disease Control and Prevention (CDC) Cholesterol Reference Method Laboratory Network (CRMLN) has assured the accuracy of these measurements for over 20 years using beta quantification (BQ) method as reference measurement procedure (RMP) for high- and low-density lipoprotein cholesterol (HDL-C, LDL-C). Only limited data exist about the performance of the BQ RMP. METHODS: Bottom fraction cholesterol (BFC), HDL-C, and LDL-C results after ultracentrifugation from the CDC lipid reference laboratory and the Japanese CRMLN laboratory were compared using 280 serum samples measured over the past 15 years. Data were compared statistically using method comparison and bias estimation analysis. RESULTS: Regression analysis between CDC (x) and Osaka (y) for BFC, HDL-C, and LDL-C were y=0.988x+1.794 (R(2)=0.997), y=0.980x+1.118 (R(2)=0.994), and y=0.987x+1.200 (R(2)=0.997), respectively. The Osaka laboratory met performance goals for 90% to 95% of the CDC reference values. CONCLUSIONS: The BQ method by the Osaka CRMLN laboratory is highly accurate and has been stable for over 15 years. Accurate measurement of BFC is critical for the determination of LDL-C.

Validation of homogeneous assays for HDL-cholesterol using fresh samples from healthy and diseased subjects.

BACKGROUND: High-density lipoprotein-cholesterol (HDL-C) is a negative risk factor for cardiovascular events. Although several homogeneous HDL-C assays are available, their accuracy has not been validated, particularly in subjects with disease. We aimed to clarify whether HDL-C concentrations measured by homogeneous assays [HDL-C (H)] agree with those determined by the reference measurement procedures [HDL-C (RMP)] using ultracentrifugation and precipitation with heparin-manganese reagent in fresh clinical samples. METHODS: HDL-C concentrations in samples from 48 healthy subjects and 119 subjects with disease were determined using 12 homogeneous assays and RMPs. RESULTS: All reagents showed excellent intra- and inter-assay CVs (<2.23%) for two pooled sera. Furthermore, the mean bias was within ± 1.0% in nine reagents using samples from healthy subjects and in eight reagents using samples from subjects with disease. In a single HDL-C (H) determination, the total error requirement of the National Cholesterol Education Program (95% of results < 13%) was fulfilled in nine reagents using samples from healthy subjects and six reagents in those from subjects with disease. Error component analysis revealed that only one reagent exceeded ± 10% total error in samples from healthy subjects, whereas four reagents exceeded this error in samples from subjects with disease. Correlations between HDL-C (H) and HDL-C (RMP) revealed that the slopes were within 1.00 ± 0.06 in six reagents in healthy subjects, and eight reagents in subjects with disease. CONCLUSIONS: Except for three reagents, HDL-C (H) agrees well with HDL-C (RMP) in subjects with common disease, but not in those with extremely low HDL-C or abnormal HDL composition.

A multicenter study on the precision and accuracy of homogeneous assays for LDL-cholesterol: comparison with a beta-quantification method using fresh serum obtained from non-diseased and diseased subjects.

BACKGROUND: Homogeneous assays for low-density lipoprotein-cholesterol (LDL-C) have good precision and are pretreatment-free procedures. However, their accuracies have been questioned, especially in diseased subjects. In this study, we aimed to verify whether LDL-C levels determined by homogeneous assays [LDL-C (H)] agree with those determined by a beta-quantification method [LDL-C (BQ)] in fresh clinical samples. METHODS: We determined LDL-C levels in 49 non-diseased and 124 diseased subjects whose triglyceride (TG) levels were less than 11.29 mmol/L (1000 mg/dL) using 12 homogeneous assays and a BQ method simultaneously. RESULTS: In total, 30.6% of non-diseased subjects and 46.0% of diseased subjects were in the postprandial state. The maximum inter- and intra-assay CVs were 1.8% and 1.5%, and 8 reagents had a CV of 1.0% or less. The mean bias ranged from -0.5% to 1.8% for non-diseased subjects and from -0.7% to 1.6% for diseased subjects. For non-diseased subjects, all but one reagent achieved the National Cholesterol Education Program (NCEP) total error requirement in more than 90% of samples. However, for diseased subjects, the number of reagents that met this requirement was low. With some reagents, LDL-C (H) was higher than LDL-C (BQ), especially in subjects with hypertriglyceridemia. While for other reagents, the difference between the two methods was not associated with hypertriglyceridemia except for type I (n = 2) and type III hyperlipidemia (n = 1). Postprandial sampling was not the main factor for discordant results. CONCLUSIONS: LDL-C (H) agrees with LDL-C (BQ) in non-diseased subjects, but exhibits positive bias for subjects with hypertriglyceridemia in diseased subjects for some reagents.

[ISO 15189 accreditation and future perspectives-Chairmen's introductory remarks].

Recently, transparency of the organization administration and patient-centered medical care such as patient service and satisfaction have been demanded in the medical field. The role of the clinical laboratory, one of the organizations in the medical field, is to provide quality laboratory data to improve diagnosis and treatment. Other than clinical laboratory facilities, education and the ability of staff to use it, the management of the organization must be appropriate to produce high quality laboratory data. International guidance on how to manage a laboratory is shown in ISO 15189. Clinical laboratories with ISO accreditation in Europe, Australia and Asia are increasing. On the other hand, only 60 institutions (10 national university hospitals, 4 public private university hospitals, 12 private hospitals and 34 referral laboratories) are accredited in Japan. Six speakers spoke at this symposium about the accreditation system of ISO 15189, the experiences of the acquiring institution and the effect of acquisition, as well as the future prospects of ISO 15189. This was a good opportunity to become informed about the current situation of ISO 15189 in Japan and internationally.

[Distributions and spreads of antimicrobial drug-resistant microorganisms in Saga prefecture].

We investigated the distribution of drug-resistant organisms to clarify transmission of the organisms. Drug-resistant organisms were surveyed in 12 facilities in 4 districts of Saga prefecture for 2 years, and were analyzed by beta-lactamase typing, antimicrobial susceptibility tests and pulsed-field gel electrophoresis (PFGE). The number of isolates was 111,505 for the 2 years. Questionnaires for drug-resistant organisms revealed that Methicillin-resistant Staphylococcus aureus (MRSA) was 64.1% of S. aureus, penicillin-intermediate Streptococcus pneumoniae (PISP) or penicillin-resistant S. pneumoniae (PRSP) 60.1% of S. pneumoniae, beta-lactamase-negative ampicillin-resistent Haemophilus inflluenzae (BLNAR) 19.4% of H. influenzae, Metallo-beta-Lactamase (MBL) 0.1% of gram-negative bacilli, multi-drug resistant Pseudomonas aeruginosa (MDRP) 0.6% of P. aeruginosa and extended-spectrum beta-lactamase (ESBL) producing organisms 8.0% and 3.1% of Escherichia coli and Klebsiella pneumoniae, respectively. PFGE analysis of ESBL E. coli revealed that 33 isolates collected from 7 facilities in 3 districts belonged to the same one group, indicating that this strain is transferred between different hospitals in different saga districts. Investigations of distribution of drug-resistant organisms in not only each hospitals but also in the first and the second medical areas are important for controls of healthcare-associated infections and antibiotic prescriptions.

[Microbiological and clinical features of nine cases with nocardial infections].

Following recent advance in medical technology, the increase of immunocompromised patients results in an increase of opportunistic infections such as nocardiosis. However, little is known about relationships between clinical features of nocardial infections and each Nocardia species, especially newly identified ones. Therefore, we identified clinical isolates of Nocardia species by genetic methods and analyzed clinical features of nocardiosis. Nine clinical isolates were obtained in Kyushu University Hospital from 2005 to 2008. Six different Nocardia species were identified by 16Sr RNA: Nocardiafarcinia (n=2), Nocardia brasiliensis (n=2), Nocardia cyriacigeorgica (n=2), Nocardia transvalensis (n=1), Nocardia araoensis (n=1) and Nocardia testacea (n=1). The underlying diseases of 9 patients were pulmonary diseases(n=5), malignant diseases(n=3), collagen diseases(n=1) or primary immunodeficiency diseases (n=l). According to antimicrobial susceptibility testing, none of them was resistant to minocycline or linezolid. Among seven isolates from respiratory specimens, one was resistant to imipenem, sulfamethoxazole/trimethoprim and amikacin, two were to ciprofloxacin. Three species identified recently (N cyriacigeorgica, N. araoensis and N. testacea) were involved in this study and most of them were considered as infectious pathogens to human. These data suggested the identification of Nocardia to the species level and susceptibility testing were important for diagnosis as infectious diseases and treatments.

Enzymatic assay of phosphatidylethanolamine in serum using amine oxidase from Arthrobacter sp.

BACKGROUND: In human serum, as for phospholipids not containing choline, phosphatidylethanolamine (PE) exists approximately 5% in a whole phospholipid. PE is well known as one of the main components of biological membranes, and also plays important roles that contribute to apoptosis and cell signaling. However, it could not measure PE with other phospholipids due to a lack of choline in them. METHODS: Using an amine oxidase (EC 1.4.3.6), from Arthrobacter species, a simple and rapid enzymatic assay for measurements of PE in serum was established. That assay used the Hitachi 7170 analyzer to evaluate the analytical performance. RESULTS: The average within-run CVs were 0.38-1.27% (n=20) at 69-160 µmol/l. The correlation between values obtained with the present method (y) and the high-performance liquid chromatography (HPLC) method (x) was: y=0.944x+9.441 (r=0.977, S(y|x)=5.82, n=34). In addition, the reference interval of healthy subjects was 115±45 µmol/l. CONCLUSIONS: This new enzymatic method shows a high specificity for serum PE and can be easily applied to an automated analyzer. The present method is available as a novel marker of changes in the clinical condition of serum phospholipids.