Detection of anti-ovalbumin IgG in serum by immune complex transfer enzyme immunoassay

An immune complex transfer enzyme immunoassay for anti-ovalbumin IgG in serum is described. Serum-specific antibody was reacted simultaneously with 2,4-dinitrophenyl-bovine serum albumin-ovalbumin conjugate and ovalbumin-peroxidase conjugate. The complex formed by the three components was trapped onto polystyrene balls coated with anti-2,4-dinitrophenyl group IgG, eluted with epsilonN-2,4-dinitrophenyl-L-lysine and transferred to polystyrene balls coated with anti-human IgG-gamma-chain. Bound peroxidase activity was determined by fluorometry. This enzyme immunoassay was 300- to 1,000-fold more sensitive and more reliable than the enzyme-linked immunosorbent assay (ELISA). Anti-ovalbumin IgG was detected in 100% of healthy subjects using this method while only 14% were detected by ELISA.

A useful ELISA system for human liver-type arginase, and its utility in diagnosis of liver diseases

OBJECTIVES

To develop a new ELISA system for liver-type arginase using monoclonal antibodies against the enzyme, and to verify the utility of the arginase in diagnosis of hepatic disorders.

DESIGN AND METHODS

We have developed an enzyme-linked immunosorbent assay (ELISA), using two kinds of monoclonal antibodies (Mo6G3 and Mo9C5) for human liver-type arginase as the first and second antibodies respectively. We have also developed a new method to eliminate the influence of erythrocyte-derived arginase contamination in hemolytic samples. This ELISA was applied to specimens received from patients with acute and chronic hepatic disease and also patients who had undergone partial hepatectomy.

RESULTS

This assay is sensitive and reproducible for the measurement of liver-type arginase in the sera of patients with liver dysfunction, and enabled us to detect enzyme concentrations as low as 27 pmol/L without any processing of the samples. The assay showed within-run coefficients of variation (CV) ranging from 1.9 to 4.1% and between-day CV from 3.6 to 5.1% for arginase concentrations varying from 57.1 to 1200 pmol/L. The recovery was 113% (mean) with a range of 96 to 129%. These antibodies reacted strongly with both recombinant and native liver-type arginases, while, to some extent, with erythrocyte-derived arginase. Correction for erythrocyte-derived arginase contamination in hemolytic samples was, however, easily made by assaying peroxidase-like activity of hemoglobin. From the view of a limited localization of arginase in the liver, the marked increase of the enzyme in serum reflects initiation of liver injury, while the rapid decrease reflects termination of the damage. Such quick normalization in circulating liver-type arginase indicated another merit of the enzyme in diagnosis of liver diseases.

CONCLUSIONS

The changes in circulating liver-type arginase level could be helpful not only in the diagnosis of liver diseases but also subsequent treatment of the patients with liver damage.

[Clinical significance of anti-liver-type arginase autoantibody in blood of recipients after partial liver transplantation]

Autoantibody against human liver-type arginase was detected in blood of patients treated with partial liver transplantation and consisted of all subclasses of IgG, i.e., IgG1, IgG2, IgG3 and IgG4, and IgM. We newly constructed an ELISA system for the antibodies by the aid of arginase protein immunopurified from extracts of human liver tissues. Addition of 2.0 mol/l urea in 0.1 mol/l citrate buffer(pH 4.5) was effective for elimination of immunoglobulins, such as IgG and IgM, and rheumatoid factors adsorped non-specifically to liver-type arginase-autoantibody complexes on the plate. We found that, during a short period of about two months after operation, in successful cases, liver-type arginase increased, remarkably and repeatedly, in blood of recipients followed by elevation of IgM level within a week and also IgG2 level two or three weeks later. Thus the change in IgG2 level seemed to depend on those of the arginase and/or IgM. However, in unsuccessful cases, such fluctuation was not so clear as the successful cases. To be noteworthy was production of autoantibodies directed to liver-type arginase in blood of patients with liver injury although the arginase, as well as AST and ALT, is an enzyme which leaks out of liver tissue. Appearance of the autoantibodies in blood supports occurrence of liver injury, in part, in graft liver because the enzyme exists exclusively in the liver. Among immunoglobulins to liver-type arginase, IgG2 seemed to be the most helpful index to know rightly postoperative conditions of recipients of liver transplantation, and its measurement could be useful for long-term follow-up of the patients.

[Importance of health care work for the clinical pathologist]

Health care work should be one of the important roles of the clinical pathologist. However, we do not have specific health care programs yet. I would like to propose that the Japan Society of Clinical Pathology should become involved in the region of health care programs. In the health care programs that we discuss here, target values appropriate for healthy people to maintain their health are determined. Laboratory medicine is expected to make great contributions in this respect. I hope this session will be helpful in promoting an understanding of the importance of health care programs among our members.

Human cysteine dioxygenase gene: structural organization, tissue-specific expression and downregulation by phorbol 12-myristate 13-acetate

The organization of the human cysteine dioxygenase (CDO) gene was found to be similar to its rat counterpart, and the location of the introns in the protein structure was identical to the rat CDO gene. The major transcription start site, identified by primer extension, was located 260 bp upstream from the ATG codon. The sequence of the 5'-immediate upstream region was highly conserved between the human and rat CDO genes. The putative promoter region contained a TATA-box-like sequence, and many putative cis-acting elements including HNF5, GRE, TRE, CRE, CArG box, ARE, MBS, and NF-kB. A Northern blot analysis revealed that CDO mRNA was strongly expressed in the liver and placenta, and weakly in the heart, brain and pancreas. CDO mRNA was also detected in human hepatoblastoma HepG2 cells. The CDO mRNA level in HepG2 cells was decreased after 2 h and reached a minimum 6 h-8 h after a phorbol 12-myristate 13-acetate (PMA) treatment, and then gradually returned to the basal level.

Sensitive enzyme immunoassay for anti-beta-lactoglobulin IgG in serum

A sensitive enzyme immunoassay for anti-beta-lactoglobulin immunoglobulin G (IgG) in serum is described. Serum containing anti-beta-lactoglobulin IgG was reacted simultaneously with 2,4-dinitrophenyl-bovine serum albumin-beta-lactoglobulin conjugate and beta-lactoglobulin-peroxidase conjugate. The complex formed from the three components was trapped onto polystyrene balls coated with anti-2,4-dinitrophenyl group IgG, eluted with epsilon N-2,4-dinitrophenyl-L-lysine and transferred to polystyrene balls coated with anti-human IgG.gamma-chain IgG. Bound peroxidase activity was determined by fluorometry. This enzyme immunoassay was 100- to 1000-fold more sensitive and more reliable than the enzyme-linked immunosorbent assay (ELISA). Anti-beta-lactoglobulin IgG was detected in 91% of healthy subjects using this method.

Liver-type arginase in serum during and after liver transplantation: a novel index in monitoring conditions of the liver graft and its clinical significance

We quantified liver-type arginase in sera of 47 patients undergoing partial liver transplantation with use of an ELISA method. The level of liver-type arginase fluctuated slightly beyond the normal range in successful liver recipients, while it changed more drastically or precipitously in unsuccessful ones, accompanying or unaccompanying elevation of AST and ALT levels. A higher elevation pattern of the arginase level (above 100 ng ml-1) was observed in each of the unsuccessful recipients with critical condition, except for one patient. Other hepatic markers (LDH, ALP, and T-BIL) remained relatively unchanged until the terminal stage of deceasing patients. The finding that the liver-type arginase emerged in large quantity in the blood stream immediately after reperfusion of the liver graft indicates that the enzyme leaks out of hepatocytes damaged, presumably, by storage in the absence of circulation. A half-life of the liver-type arginase in the human blood was estimated to be 1 h, that is clearly shorter than that of AST. The short half-life of the arginase appears to be ascribable, at least partly, to formation of an immune complex with circulating autoantibody which appears in many liver recipients. These results suggest that liver-type arginase behaves uniquely in the serum among many hepatic enzymes, and could serve as a distinct marker of hepatic lesions, particularly during and after liver transplantation.

Structural organization and tissue-specific expression of the gene encoding rat cysteine dioxygenase

Cysteine dioxygenase (CDO) is a key enzyme involved in the metabolism of L-cysteine. Genomic clones containing the 5'-flanking sequence of the rat CDO gene were isolated and characterized. The CDO gene spanned about 15 kb, and comprised 5 exons. All boundaries between the exons and introns matched the GT/AG rule. The major transcription start point (tsp) was A at 213 bp upstream from the ATG codon. The 5'-flanking region contained a TATA-box-like sequence and putative cis-acting regulatory elements. The 3' end of CDO was polyadenylated at several sites. Northern blots of RNA from rat tissues revealed the highest CDO mRNA level in the liver. Significant levels were observed in the kidney, lung and brain, implying tissue-specific differences in CDO promoter function.

A chemiluminescence-flow injection analysis of serum 3-hydroxybutyrate using a bioreactor consisting of 3-hydroxybutyrate dehydrogenase and NADH oxidase

We describe a simple method for the highly sensitive chemiluminescence--flow injection analysis of 3-hydroxybutyrate in serum using a bioreactor column consisting of the two immobilized enzymes, 3-hydroxybutyrate dehydrogenase and NADH oxidase. The method was based on measuring the level of chemiluminescence formed by the reaction of a luminol-hexacyanoferrate mixture with hydrogen peroxide. The hydrogen peroxide was produced by the NADH oxidase reaction from NADH which was formed in the conversion of 3-hydroxybutyrate to acetoacetate by the 3-hydroxybutyrate dehydrogenase reaction. Among three immobilized enzyme columns, a coimmobilized, small 3-hydroxybutyrate dehydrogenase/NADH oxidase bioreactor alone (2 x 20 mm i.d.) readily hydrolyzed all of the injected 3-hydroxybutyrate into acetoacetate, although 3-hydroxybutyrate dehydrogenase catalyzed the reversible reaction. The present method generated linearity of the data up to 1.5 mM 3-hydroxybutyrate with satisfactory precision, reproducibility, and accurate reaction recoveries. The results from 3-hydroxybutyrate correlated satisfactorily with those obtained by other well-established methods. The coimmobilized 3-hydroxybutyrate dehydrogenase/NADH oxidase reactor unit showed good operational stability over a 5-week period, during which it was repeatedly used for 1500 analyses.

Enzyme immunoassay of liver-type arginase and its potential clinical application

We developed an efficient enzyme-linked immunosorbent assay (ELISA) system for measurement of human liver-type arginase in serum. A conjugate of the Fab' fragment of anti-human liver (recombinant) arginase IgG and horseradish peroxidase was used as the second antibody. This assay is highly specific, sensitive, and reproducible, enabling us to detect arginase at concentrations as low as several micrograms per liter without any prior processing of serum. The reaction is linear up to 200 micrograms/L. The arginase concentration in serum, as determined by this method, increased markedly and temporarily at the time of surgical operation or later injury to the liver. The increase was accompanied or followed by increases in serum concentrations of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase, suggesting that the arginase emerged from damaged hepatocytes. In view of a limited tissue distribution of liver-type arginase, our ELISA system may be useful in diagnosis of various hepatic disorders as well as follow-up of postoperative conditions of patients.

Enzyme immunoassay of liver-type arginase and its potential clinical application

We developed an efficient enzyme-linked immunosorbent assay (ELISA) system for measurement of human liver-type arginase in serum. A conjugate of the Fab' fragment of anti-human liver (recombinant) arginase IgG and horseradish peroxidase was used as the second antibody. This assay is highly specific, sensitive, and reproducible, enabling us to detect arginase at concentrations as low as several micrograms per liter without any prior processing of serum. The reaction is linear up to 200 micrograms/L. The arginase concentration in serum, as determined by this method, increased markedly and temporarily at the time of surgical operation or later injury to the liver. The increase was accompanied or followed by increases in serum concentrations of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase, suggesting that the arginase emerged from damaged hepatocytes. In view of a limited tissue distribution of liver-type arginase, our ELISA system may be useful in diagnosis of various hepatic disorders as well as follow-up of postoperative conditions of patients.

Substrate specificity and distribution of UDP-GalNAc:sialylparagloboside N-acetylgalactosaminyltransferase in the human stomach

The detailed substrate specificity of the UDP-GalNAc:sialylparagloboside N-acetylgalactosaminyltransferase to form the Sd(a+) blood group active carbohydrate determinant GalNAc beta 1-4(NeuAc alpha 2-3)Gal was studied using a membrane fraction prepared from human gastric fundic mucosa. Various sialosylated oligosaccharides and gangliosides were examined as acceptor substrates. Oligosaccharide substrates were fluorescence-labelled with 2-aminopyridine, and the transferase activity was quantified by h.p.l.c. using a reversed-phase column. The structures of the products were determined by glycosidase degradation and proton n.m.r. 3'-Sialyl-lactose (II3NeuAcLac), 3'-sialyl-lactotetraose (IV3NeuAcLc4), and 3'-sialyl-lactoneotetraose (IV3NeuAcnLc4) were good substrates for the beta 1-4GalNAc transferase in gastric fundic mucosa, but 6'-sialyl-lactoneotetraose (IV6NeuAcnLc4) or 6'-sialyl-lactose (II6NeuAcLac) were not. Gangliosides with a terminal NeuAc alpha 2-3Gal residue such as GM3, sialylparagloboside, GM1b and GD1a were also studied. The activity of beta 1-4GalNAc transfer to sialylparagloboside was much higher than that to GM2, GM1b or GD1a in spite of them having the same terminal residue. Measurement of the activity of the beta 1-4GalNAc transferase in biopsy specimens demonstrated that the activity was localized in gastric fundic mucosa and was absent in pyloric mucosa, intestinal metaplasia and gastric cancer tissue. Thus the beta 1-4GalNAc transferase present specifically in fundic mucosa required a NeuAc alpha 2-3Gal residue connected to either type-1-chain or type-2-chain oligosaccharides. In glycolipids, the acceptor specificity was restricted to NeuAc alpha 2-3Gal beta 1-4GlcNAc because the NeuAc alpha 2-3Gal beta 1-3GalNAc structure in ganglio-series glycolipids was not a good acceptor substrate.

Use of various types of column reactors for flow-injection analysis

Two or three different kinds of immobilized enzymes can be aligned in a minireactor so that sequential enzymatic reactions are carried out from upstream to downstream during flow-injection analysis. A lactate oxidase-catalase reactor, used as precolumn for removing pre-existing lactate in serum before the lactose dehydrogenase (LDH) reactions, was useful for the determination of serum LDH activity, which did not require any blank correction. A sequential glutamate dehydrogenase-glutamate oxidase reactor was also useful for a novel chemiluminometric determination of ammonia. On the other hand, a co-immobilized creatininase-creatinase-sarcosine oxidase reactor, in spite of containing creatininase which catalyses the reversible reaction, was the most efficient for the determination of serum creatinine.

Absence of erythrocyte arginase protein in Japanese patients with hyperargininemia

In Japan, hyperargininemia has been reported in only 5 unrelated families and four patients are alive at present. In this study we examined arginase protein in erythrocytes of these Japanese patients using two analytical methods of immunoblotting and two-dimensional gel electrophoresis. Immunoblotting study with anti-E. coli-expressed human liver arginase rabbit IgG revealed lack of cross-reacting materials in the erythrocyte lysates from these patients. On two-dimensional gels, arginase protein was detected in any control subject, but it was completely absent in all the patients studied. These results suggest that either arginase protein in erythrocytes is not produced or it is structurally labile in these patients.

Determinations of lactate and lactate dehydrogenase activity in serum with the flow injection analysis system involving immobilized enzyme column and chemiluminescence

The methods for the highly sensitive flow injection analysis of lactate and lactate dehydrogenase (LDH) activity in serum using immobilized enzymes in column form and chemiluminescence detection which does not require a blank correction are described. The methods were based on the determination of chemiluminescence formed by the reaction of a luminol-ferricyanide mixture with hydrogen peroxide. This hydrogen peroxide was produced by the lactate oxidase (LOD) reaction from lactate, which was in serum or was produced by the action of LDH in serum. The action of LDH in a flow injection analysis system was performed for 2 min in an incubation coil placed parallel to the substrate-buffer line between the LOD column and the LOD/catalase column. Endogenous lactate in serum was removed by an immobilized LOD/catalase column prior to the action of LDH. The present method gave perfect linearity of the data up to 5.6 mmol/liter for lactate and 1840 IU/liter for LDH activity with satisfactory precision, reproducibility, and accurate reaction recoveries. The results from the lactate and LDH activity correlated satisfactorily with those obtained by other well-established methods.

Expression of human liver arginase in Escherichia coli. Purification and properties of the product

Arginase is an enzyme that catalyses the hydrolysis of arginine to urea and ornithine. It is abundantly present in the liver of ureotelic animals (i.e. those whose excretion is characterized by the excretion of uric acid as the chief end-product of nitrogen metabolism), but its purification has hitherto not been simple, and the yield not high. Starting with a partially truncated cDNA for human liver arginase recently made available, we constructed an expression plasmid that had tandemly linked tac promotors placed upstream of a full-length cDNA. By selecting Escherichia coli strain KY1436 as the host micro-organism, we established an efficient system for the production of human liver arginase protein. Chromatographies on CM-Sephadex G-150, DEAE-cellulose and Sephadex G-150, followed by preparative agar-gel electrophoresis, yielded 10 mg of apparently homogeneous enzyme protein from 1 g (wet wt.) of E. coli cells. E. coli-expressed human liver arginase had chemical, immunological and most catalytic properties indistinguishable from those of purified human erythrocyte arginase. However, E. coli-expressed arginase was a monomer of Mr 35,000, whereas the purified erythrocyte arginase was trimer of Mr 105,000. They differed also in pH- and temperature-stabilities. Gel-filtration experiments with these two purified arginases under various conditions, as well as with unfractionated human liver and erythrocyte cytosol preparations, indicated that the native form of human arginase should be of Mr 35,000, and that the trimeric appearance of human erythrocyte arginase after purification was an artifact of the purification procedures. It was thus concluded that, in Nature, the liver and erythrocyte arginases are identical proteins.

A chemiluminometric method for NADPH and NADH using a two-enzyme bioreactor and its application to the determination of magnesium in serum

Chemiluminometric methods are described for the automated flow injection analysis of NADPH and NADH using an immobilized enzyme column reactor and serum magnesium. This application is for the clinical analysis of NADPH and NADH. The reactor for NADPH and NADH contains immobilized L-glutamate dehydrogenase and L-glutamate oxidase, and that for serum magnesium immobilized hexokinase, glucose-6-phosphate dehydrogenase, L-glutamate dehydrogenase and L-glutamate oxidase. When the sample is introduced into the four-enzyme bioreactor, hydrogen peroxide is produced in proportion to the concentration of serum magnesium by the successive reactions. A co-immobilized hexokinase/glucose-6-phosphate dehydrogenase/glutamate dehydrogenase column reactor gave better efficiency compared with an enzyme column which was prepared by packing co-immobilized hexokinase/glucose-6-phosphate dehydrogenase and immobilized glutamate dehydrogenase to make two layers. Magnesium in serum was determined with 1 microL of the sample without carry-over and for an assay time of approximately 15 s. The present method is sensitive (detection limit 0.1 nmol) because Mg2+ is recycled in a column, and gives perfect linearity of the data up to 3.0 mmol/L with satisfactory precision, reproducibility, and accurate reaction recoveries.

A flow injection analysis system involving immobilized NADH oxidase in column form for clinical analysis

A highly sensitive FIA system for chemiluminometric determination of reduced coenzyme, NADH, was developed, using immobilized NADH oxidase from Brevibacterium ammoniagenes. The enzyme catalyzed the oxidation of NADH generating hydrogen peroxide which emitted chemiluminescence when mixed with luminol and potassium ferricyanide. The immobilized enzyme reactor was a mini-column, measuring 1 or 2 mm in inner diameter and 20 mm in length, and the sample volume was only 1 microliter per assay, with a feeding speed of one sample per min and a lowest detection limit of 10 pmol NADH. A FIA system was also developed for the determination of magnesium in human serum, using an enzyme column reactor with simultaneously coimmobilized hexokinase, D-glucose-6-phosphate dehydrogenase, and NADH oxidase. The performance of the system was as satisfactory as a routine colorimetric assay, but with much higher sensitivity.

Monoclonal antibody inhibiting creatine kinase MM3 but not isoform MM1

Monoclonal antibody CKM-G01 inhibited greater than 99% of the activity of porcine and human creatine kinase(CK)-MM isoenzyme purified from muscle. However, it inhibited only 54% of CK-MM in human serum. Chromatofocusing of serum CK-MM showed that CKM-G01 inhibited 100% of MM3 but not isoform MM1. CKM-G01 inhibited CK-MM2 by 57%. CKM-G01 specifically inhibited only the original CK-M subunit and not the subunit modified by removal of C-terminal lysine by carboxypeptidase N. CKM-G01 can be used for assay of CK isoforms. We devised a new diagnostic reagent involving it, which requires no analytical separation of isoforms, based on the immunoinhibition method, and applied it to early diagnosis of acute myocardial infarction. The "inhibition index," (inhibited CK activity/total CK activity) x 100, increased more rapidly than did total CK and CK-MB. Evidently this diagnostic reagent can be used for easy, early diagnosis of acute myocardial infarction.

Monoclonal antibody inhibiting creatine kinase MM3 but not isoform MM1

Monoclonal antibody CKM-G01 inhibited greater than 99% of the activity of porcine and human creatine kinase(CK)-MM isoenzyme purified from muscle. However, it inhibited only 54% of CK-MM in human serum. Chromatofocusing of serum CK-MM showed that CKM-G01 inhibited 100% of MM3 but not isoform MM1. CKM-G01 inhibited CK-MM2 by 57%. CKM-G01 specifically inhibited only the original CK-M subunit and not the subunit modified by removal of C-terminal lysine by carboxypeptidase N. CKM-G01 can be used for assay of CK isoforms. We devised a new diagnostic reagent involving it, which requires no analytical separation of isoforms, based on the immunoinhibition method, and applied it to early diagnosis of acute myocardial infarction. The "inhibition index," (inhibited CK activity/total CK activity) x 100, increased more rapidly than did total CK and CK-MB. Evidently this diagnostic reagent can be used for easy, early diagnosis of acute myocardial infarction.

Purification and properties of human erythrocyte arginase

An efficient method for purification of human erythrocyte arginase was developed. This method included two new procedures, hydrophobic chromatography and immunoaffinity chromatography, and yielded 0.7 mg of homogeneous arginase protein from 2.1 L of haemolysate. The molecular weight of native arginase was estimated to be 105,000 by gel filtration on a Sephadex G-150 column, and that of its subunit 35,000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. This indicates that the native enzyme is composed of three homologous subunits. Amino acid composition of human erythrocyte arginase was found to be very similar to that of liver arginase of several other mammals. After dialysis against distilled water, the purified arginase still retained its enzymatic activity which was decreased by EDTA and reversibly restored by Mn(II) ion. A specific polyclonal antibody for use in an immunoassay was also produced. This antibody revealed one single band on immunoelectrophoretic analysis of the acetone powder extract, suggesting absence of arginase isoenzymes in human erythrocytes.

A chemiluminescence automatic analyser for the measurement of biological compounds

A compact automated analyser which could analyse constituents in biological fluids with a small sample volume and in a short time has been developed. The instrument was composed of a flow injection analysis system equipped with chemiluminometric detection and an immobilized enzyme column reactor used in combination. Chemiluminescence has high sensitivity, and its reaction proceeds very quickly. Furthermore, an immobilized enzyme column reactor can produce a sufficient amount of hydrogen peroxide from compounds in serum in a short time. When enzymes are used as reagents for the analysis of substances in blood or blood serum, the final signals emitted by different enzyme reactions are usually not only hydrogen peroxide but also ammonia, NAD(P)H and so on. However, the practical chemiluminescence method for ammonia and NAD(P)H has not been established. We have discovered a new practical method for ammonia and NAD(P)H using an enzyme column reactor consisting of both immobilized L-glutamate dehydrogenase and L-glutamate oxidase. The determinations of glucose and uric acid in serum by chemiluminometry after production of hydrogen peroxide by the respective oxidases are presented. A newly chemiluminometric determination of ammonia, NAD(P)H and its applications to other enzymatic analyses that give ammonia and NAD(P)H as a final signal are also described.

Monoclonal and polyclonal antibodies against porcine mitochondrial aspartate aminotransferase: their inhibition modes and application to enzyme immunoassay

Monoclonal and polyclonal antibodies against porcine mitochondrial aspartate aminotransferase (m-AST) were prepared in order to study their effect on the kinetics of the enzyme and their possible use as diagnostic reagents. The most stable hybridoma clone, designated MH-1, was selected and cultured for mass production of the monoclonal antibody MA-1. MA-1 was purified by affinity chromatography with m-AST as a ligand. The m-AST activity was inhibited uncompetitively by preincubation with MA-1, but preincubation with the polyclonal antibody uncompetitively by preincubation with MA-1, but preincubation with the polyclonal antibody raised in a rabbit resulted in noncompetitive inhibition of the enzyme. These results suggest the usefulness of a monoclonal antibody for studying the mechanism of catalysis. Sandwich enzyme immunoassay methods for m-AST using both polyclonal and monoclonal antibody-coated polystyrene balls were established and permitted the determination of porcine m-AST on the order of 10(-11) and 10(-10)M, respectively.

Specific enzymatic assay method for homocysteine and its application to the screening of neonatal homocystinuria

A simple and specific enzymatic assay method for homocysteine is described. The method is based on the formation of S-adenosylhomocysteine from adenosine and homocysteine through the catalysis of S-adenosylhomocysteine hydrolase (EC 3.3.1.1), followed by its separation by high-performance liquid chromatography. The results for human blood, serum, and urine and those extracted from filter paper showed good correlation with those obtained on measurement with a conventional amino acid analyzer, which demonstrates that the method is useful for neonatal screening for homocystinuria.

Direct spectrophotometry of magnesium in serum after reaction with hexokinase and glucose-6-phosphate dehydrogenase

We describe a simple method for determining magnesium in serum by using hexokinase (EC 2.7.1.1) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49). The method is based on determination of the reaction rate of hexokinase activated by Mg2+, which participates in the hexokinase reaction as the substrate in the form of a Mg X ATP2- complex. The reaction rate is determined from the change in absorbance at 340 nm as NADPH is produced by the action of glucose-6-phosphate dehydrogenase. This simple and rapid spectrophotometric method does not require expensive instrumentation, but results correlate satisfactorily with those obtained by atomic absorption spectroscopy. Thus, the present method gives a "true" value for magnesium in serum, a value appreciably lower than that obtained by an earlier colorimetric method, the Xylidyl Blue II method (Biochem Med 7: 208-217, 1973), which lacks specificity.

Direct spectrophotometry of magnesium in serum after reaction with hexokinase and glucose-6-phosphate dehydrogenase

We describe a simple method for determining magnesium in serum by using hexokinase (EC 2.7.1.1) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49). The method is based on determination of the reaction rate of hexokinase activated by Mg2+, which participates in the hexokinase reaction as the substrate in the form of a Mg X ATP2- complex. The reaction rate is determined from the change in absorbance at 340 nm as NADPH is produced by the action of glucose-6-phosphate dehydrogenase. This simple and rapid spectrophotometric method does not require expensive instrumentation, but results correlate satisfactorily with those obtained by atomic absorption spectroscopy. Thus, the present method gives a "true" value for magnesium in serum, a value appreciably lower than that obtained by an earlier colorimetric method, the Xylidyl Blue II method (Biochem Med 7: 208-217, 1973), which lacks specificity.

Automated assay of creatinine in serum as simplified by the use of immobilized enzymes, creatinine deiminase, and glutamate dehydrogenase

A method for the automated analysis of creatinine in serum using immobilized enzymes in column form which does not require a blank correction and can be run in a single buffer of pH 7.5 is described. The method was based on the determination of ammonia formed by the action of creatinine deiminase. Endogenous ammonia in serum was removed by an immobilized glutamate dehydrogenase column prior to the action of creatinine deiminase also immobilized and used in column form. The present method was found to give perfect linearity of the data up to 0.10 g creatinine/liter with satisfactory precision, reproducibility, and accurate reaction recoveries. The immobilized enzyme reactor unit showed good operational stability for a 2-month period, during which time it was repeatedly used for analyses over 2000 times. The results correlated satisfactorily with those obtained by other well-established methods.