[Bicentennial of catalase research, 1818-2018]

L. J. Thénard and J. L. Gay-Lussac discovered hydrogen peroxide in 1818. Later, Thénard noticed that animal and plant tissues decompose hydrogen peroxide. The substance which is responsible for this reaction was named as catalase by O. Loew in 1900. The catalase enzyme was regarded as a diagnostic and a tumour marker in the late years of the 19th century and in the early years of the 20th century. Acatalasemia, an inherited deficiency of enzyme catalase, was studied in Japan, Switzerland and Hungary. The recent findings on catalase are focusing on the effects of reactive oxygen species and on the association of acatalasemia and diabetes mellitus. Orv Hetil. 2018; 159(24): 959-964.

[Acatalasemia and type 2 diabetes mellitus]

The catalase enzyme decomposes the toxic concentrations of hydrogen peroxide into oxygen and water. Hydrogen peroxide is a highly reactive small molecule and its excessive concentration may cause significant damages to proteins, deoxyribonucleic acid, ribonucleic acid and lipids. Acatalasemia refers to inherited deficiency of the catalase enzyme. In this review the authors discuss the possible role of the human catalase enzyme, the metabolism of hydrogen peroxide, and the phenomenon of hydrogen peroxide paradox. In addition, they review data obtained from Hungarian acatalasemic patients indicating an increased frequency of type 2 diabetes mellitus, especially in female patients, and an early onset of type 2 diabetes in these patients. There are 10 catalase gene variants which appear to be responsible for decreased blood catalase activity in acatalasemic patients with type 2 diabetes. It is assumed that low levels of blood catalase may cause an increased concentration of hydrogen peroxide which may contribute to the pathogenesis of type 2 diabetes mellitus.

A simple method for examination of polymorphisms of catalase exon 9: rs769217 in Hungarian microcytic anemia and beta-thalassemia patients

Catalase decreases the high, toxic concentrations of hydrogen peroxide but it lets the physiological, low concentrations in the cells mainly for signaling purposes. Its decreased activity may contribute to development of several pathological conditions. Catalase mutations occur frequently in exon 9, these were examined with different, complicated and costly methods. The aim of the current study was to evaluate a method for screening of polymorphisms in catalase exon 9. We used the slab gel electrophoresis of PCR amplicons without denaturation and silver staining for visualization of the DNA bands. We detected extra DNA bands in the 400-800 bp region of the catalase exon 9. Their single stranded nature was proved with nucleotide sequence analyses, comparison with the standard SSCP, staining with Sybr Green II and Sybr Green I, ethidium bromide, no digestion with RFLP (BstX I), and digestion with plant nuclease. We used this method for examination of polymorphisms of catalase exon 9 in microcytic anemia and beta-thalassemia patients. The lowest blood catalase activities were detected in microcytic anemia and beta-thalassemia patients with the TT genotypes of the C111T polymorphism. This method was sensitive for detection of G113A acatalasemia mutation, but poorly detected C37T and G5A acatalasemia mutations.

Decreased blood catalase activity is not related to specific beta-thalassemia mutations in Hungary

INTRODUCTION

Thalassemia erythrocytes are exposed to oxidative stress especially to hydrogen peroxide, which is regulated with the enzyme catalase. The aim of this study was to examine blood catalase activity and the relationship of blood catalase and beta-thalassemia gene mutations.

METHODS

Blood catalase activity, hemoglobin, HbA(2) , HbF, and beta-globin gene mutations were determined in 43 Hungarian patients with beta-thalassemia trait.

RESULTS

Compared to controls, the beta-thalassemia trait patients showed a low mean (P < 0.001) of blood catalase (men: 84 ± 29 MU/L vs. sex-matched controls: 118 ± 18 MU/L and women: 74 ± 18 MU/L vs. 108 ± 114 MU/L) and a low mean of blood catalase-to-blood hemoglobin ratio (men: 0.72 ± 0.22 MU/g vs. 0.85 ± 0.12 MU/g, women: 0.77 ± 0.26 MU/g vs. 0.84 ± 0.11 MU/g). The HbA(2) determination showed high sensitivity and specificity for the detection of beta-thalassemia trait patients. Mutation analyses revealed 13 beta-thalassemia trait mutations, of which six have not been reported before in Hungarian beta-thalassemia trait patients. Each group of mutations revealed decreased (P < 0.01) mean of blood catalase and catalase-to-hemoglobin ratio. Acatalasemia mutations were not found in beta-thalassemia trait patients.

CONCLUSION

The decrease in blood catalase activity might be due to the damaging effects of free radicals on the catalase protein. Consequently, these beta-thalassemia trait patients may be relatively susceptible to damage caused by oxidative stress.

Analytical problems in determination of hemoglobin A 1c and the different ways of its interpretation

A glikált proteinek a glükóz és a fehérjék aminosava között lejátszódó nem enzimatikus reakció termékei. A hemoglobin-A 1c a glükóz és a hemoglobin mindkét béta-láncának N-terminális valinja közötti reakció eredményeként képződik, és a koncentrációja a vörösvértestek életidejének és a vér glükózkoncentrációjának függvénye. Az utóbbinak tulajdoníthatóan az előző 6–8 hét integráltglükóz-koncentrációját jelzi. A HbA 1c -t a glykaemia hosszabb távú monitorozására alkalmas, valamint a diabetes komplikációinak kockázati tényezőjeként is szolgál. A HbA 1c -mérési eredmény az előzőkön túlmenően függ még a vér egyéb szénhidrátjaitól és más alkotóitól, a meghatározási módszertől, illetve annak kalibrálási módjától. Nemzetközi társaságok (IFCC, ADA) dolgoztak ki ajánlásokat (NGSP, DDCT, IFCC) a HbA 1c -meghatározás standardizálására. Az eredmény megadására javasolja az NGSP a százalékot (g HbA 1c /g hemoglobin) és az IFCC az SI egységet (mmol HbA 1c /mol HbA). Több közleményben található olyan statisztikai módszerrel meghatározott egyenlet, amelynek segítségével a HbA 1c -ből az előző 6–8 hét átlagos glükózkoncentrációja (eADAG) megbecsülhető. Az eljárás klinikai relevanciáját több szerző még nem látja teljesen megalapozottnak.

[Rasburicase therapy may cause hydrogen peroxide shock]

Hyperuricemia contributes to the pathomechanism of diseases such as renal failure, gout, tumor lysis syndrome and metabolic syndrome. Tumor lysis syndrome is a complication of malignancies caused by massive tumor cell lysis due to either spontaneous tumor cell lysis or to different therapies and it may cause hyperuricemia. Recently, for treatment of hyperuricemia the recombinant urate oxidase (rasburicase) therapy has been used. This enzyme converts uric acid with high affinity into soluble allantoin which is eliminated by the kidneys. In this reaction high concentration of hydrogen peroxide is generated. This hydrogen peroxide could cause hemolysis and especially methemoglobin formation, in case of glucose-6-phosphate-dehydrogenase and catalase deficiencies. Therefore it is recommended that these enzymes are determined before therapy. For monitoring of rasburicase therapy the determination of serum uric acid concentration is used. More than 95 per cent of Hungarian clinical laboratories are using the uricate oxidase/peroxidase reactions and hydrogen peroxide measurements in the uric acid assays. These assays may be interfered by ascorbic acid and hydrogen peroxide which is generated by rasburicase either in vivo or in vitro.

Catalase deficiency may complicate urate oxidase (rasburicase) therapy

Patients with low (inherited and acquired) catalase activities who are treated with infusion of uric acid oxidase because they are at risk of tumour lysis syndrome may experience very high concentrations of hydrogen peroxide. They may suffer from methemoglobinaemia and haemolytic anaemia which may be attributed either to deficiency of glucose-6-phosphate dehydrogenase or to other unknown circumstances. Data have not been reported from catalase deficient patients who were treated with uric acid oxidase. It may be hypothesized that their decreased blood catalase could lead to the increased concentration of hydrogen peroxide which may cause haemolysis and formation of methemoglobin. Blood catalase activity should be measured for patients at risk of tumour lysis syndrome prior to uric acid oxidase treatment.

Effect of C111T polymorphism in exon 9 of the catalase gene on blood catalase activity in different types of diabetes mellitus

Hydrogen peroxide plays a major role in the pathomechanism of diabetes mellitus and its main regulator is enzyme catalase. The blood catalase and the C111T polymorphism in exon 9 was examined in type 1, type 2 and gestational diabetes mellitus. Compared to the control group (104.7 +/- 18.5 MU/l) significantly decreased (p < 0.001) blood catalase activities were detected in type 2 (71.2 +/- 14.6 MU/l), gestational (68.5 +/- 12.2 MU/l) diabetes mellitus and without change in type 1 (102.5 +/- 26.9 MU/l). The blood catalase decreased (p = 0.043) with age for type 2 diabetics and did not change (p>0.063) for type 1, gestational diabetic patients and controls. Blood catalase showed a weak association with hemoglobin A1c for type 1 diabetic patients (r = 0.181, increasing). The mutant T allele was increased in type 1 and gestational diabetes mellitus, and CT+TT genotypes showed decreased blood catalase activity for type 1 and increased activities for type 2 diabetic patients. The C111T polymorphism may implicate a very weak effect on blood catalase activity in different types of diabetes mellitus.

Detection of a novel familial catalase mutation (Hungarian type D) and the possible risk of inherited catalase deficiency for diabetes mellitus

The enzyme catalase is the main regulator of hydrogen peroxide metabolism. Recent findings suggest that a low concentration of hydrogen peroxide may act as a messenger in some signalling pathways whereas high concentrations are toxic for many cells and cell components. Acatalasemia is a genetically heterogeneous condition with a worldwide distribution. Yet only two Japanese and three Hungarian syndrome-causing mutations have been reported. A large-scale (23 130 subjects) catalase screening program in Hungary yielded 12 hypocatalasemic families. The V family with four hypocatalasemics (60.6 +/- 7.6 MU/L) and six normocatalasemic (103.6 +/- 23.5 MU/L) members was examined to define the mutation causing the syndrome. Mutation screening yielded four novel polymorphisms. Of these, three intron sequence variations, namely G-->A at the nucleotide 60 position in intron 1, T-->A at position 11 in intron 2, and G-->T at position 31 in intron 12, are unlikely to be responsible for the decreased blood catalase activity. However, the novel G-->A mutation in exon 9 changes the essential amino acid Arg 354 to Cys 354 and may indeed be responsible for the decreased catalase activity. This inherited catalase deficiency, by inducing an increased hydrogen peroxide steady-state concentration in vivo, may be involved in the early manifestation of type 2 diabetes mellitus for the 35-year old proband.

Catalase enzyme mutations and their association with diseases

Enzyme catalase seems to be the main regulator of hydrogen peroxide metabolism. Hydrogen peroxide at high concentrations is a toxic agent, while at low concentrations it appears to modulate some physiological processes such as signaling in cell proliferation, apoptosis, carbohydrate metabolism, and platelet activation. Benign catalase gene mutations of 5' noncoding region (15) and intron 1 (4) have no effect on catalase activity and are not associated with disease. Catalase gene mutations have been detected in association with diabetes mellitus, hypertension, and vitiligo. Decreases in catalase activity in patients with tumors is more likely to be due to decreased enzyme synthesis rather than to catalase mutations.Acatalasemia, the inherited deficiency of catalase has been detected in 11 countries. Its clinical features might be oral gangrene, altered lipid, carbohydrate, homocysteine metabolism and the increased risk of diabetes mellitus. The Japanese, Swiss, and Hungarian types of acatalasemia display differences in biochemical and genetic aspects. However, there are only limited reports on the syndrome causing these mutations. These data show that acatalasemia may be a syndrome with clinical, biochemical, genetic characteristics rather than just a simple enzyme deficiency.

The effects of hydrogen peroxide promoted by homocysteine and inherited catalase deficiency on human hypocatalasemic patients

Elevated plasma homocysteine can generate oxygen free radicals and hydrogen peroxide. The enzyme catalase is involved in the protection against hydrogen peroxide. We examined the effect of oxidative stress promoted by homocysteine on erythrocyte metabolism (blood hemoglobin, MCV, folate, B12, serum LDH, LDH isoenzymes, haptoglobin) in the oxidative stress sensitive Hungarian patients with inherited catalase deficiency. The plasma homocysteine (HPLC method, Bio-Rad), folate, B12 (capture binding assay, Abbott), blood hemoglobin concentrations, blood catalase activity (spectrophotometric assay of hydrogen peroxide), and MCV values were determined in 7 hypocatalasemic families including hypocatalasemic (male:12, female:18) patients and their results were compared to those of the normocatalasemic (male:17 female: 12) family members. We found decreased (p <.036) folate (ng/ml) concentrations (male hypocatalasemic 5.44 +/- 2.81 vs. normocatalasemic 7.56 +/- 1.97, female 5.01 +/- 1.93 vs. 6.61 +/- 1.91), blood hemoglobin (p <.010, male:140.2 +/- 11.0 vs. 153.6 +/- 11.6 g/l, female: 128.4 +/- 10.9 vs. 139.6 +/- 9.2 g/l). Increased levels of MCV (p <.001) were detected in hypocatalasemic patients (male: 98.6 +/- 3.4 vs. 90.1 +/- 7.5 fl, female: 95.9 +/- 3.9 vs. 90.1 +/- 2.5 fl), plasma homocysteine (p <.049, male: 9.72 +/- 3.61 vs. 7.36 +/- 2.10 umol/l, female: 9.06 +/- 3.10 vs. 6.84 +/- 2.50 umol/l) and not significant (p >.401) plasma B12 (male: 336 +/- 108 vs. 307 +/- 76 pg/ml, female: 373 +/- 180 vs. 342 +/- 75 pg/ml). The serum markers of hemolysis (LDH, LDH isoenzymes, haptoglobin) did not show significant (p >.228) signs of oxidative erythrocyte damage. We report firstly on increased plasma homocysteine concentrations in inherited catalase deficiency. The increased plasma homocysteine and inherited catalase deficiency together could promote oxidative stress via hydrogen peroxide. The patients with inherited catalase deficiency are more sensitive to oxidative stress of hydrogen peroxide than the normocatalasemic family members. This oxidative stress might be responsible for the decreased concentration of the blood hemoglobin via the oxidation sensitive folate and may contribute to the early development of arteriosclerosis and diabetes in these patients.

[Proteomics in clinical enzymology: polymorphism of creatine kinase and alkaline phosphatase]

INTRODUCTION

The clinical proteomics is dedicated to the use of the proteomics in the clinical laboratory science.

AIMS

Examples for the importance of clinical proteomics are provided by studies on the polymorphisms of creatine kinase and alkaline phosphatase enzymes.

METHODS

The different (immunoinhibition, electrophoretic, immunochemistry) assays for determination of a cardiac marker (creatine kinase 2) are compared in hospital patients. Isoform analysis of alkaline phosphatase is performed in benign, transient hyperphosphatasemia.

RESULTS

The author reviews recent knowledge on polymorphism of creatine kinase (isoenzymes, isoforms, macro types), and alkaline phosphatase (isoenzymes, their cancer related variants, isoforms). The origin of falsely high cardiac marker (creatine kinase 2) determined by the immunoinhibition assay could be related to the presence of macro creatine kinase (both types), creatine kinase isoenzyme 1, and their mixtures. After reviewing the recent findings on the syndrome of benign, transient hyperphosphatasemia, a case of a 1-year-old Hungarian boy with this syndrome is presented.

CONCLUSIONS

The author points out that the appropriate use of clinical proteomics (the polymorphisms of creatine kinase and alkaline phosphatase enzymes) may improve the diagnostic efficiency of the clinical laboratory tests.

A new type of inherited catalase deficiencies: its characterization and comparison to the Japanese and Swiss type of acatalasemia

Thirteen Hungarian families that exhibited inherited catalase deficiencies have been detected. Differences between the deficiencies reported from Hungary and the previously reported Swiss acatalasemia were characterized using biochemical analysis of the catalase proteins. Molecular biological methods were used to compare the previously reported types of catalase deficiencies in Japan and the Hungarian deficiencies. Three mutations (a GA insertion in exon 2, a G insertion in exon 2, and a T to G substitution in intron 7) are responsible for decreased catalase activity in 7 of the 13 Hungarian kindreds; the other 6 families have not yet been characterized. These are not the mutations observed in Japan. Changes in lipid and carbohydrate metabolism and the high incidence (12.7%) of diabetes mellitus in the Hungarian kindreds suggest that individuals with inherited catalase deficiency are at risk of atherosclerosis and diabetes mellitus. The Hungarian subjects were detected during screening of a large population for catalase activity; no overt disease state was associated with the deficiencies. We hypothesize that the increased risk of disease may be due to prolonged exposure to elevated levels of blood hydrogen peroxide due to the lack of normal removal of hydrogen peroxide by blood catalase.

A novel catalase mutation detected by polymerase chain reaction-single strand conformation polymorphism, nucleotide sequencing, and western blot analyses is responsible for the type C of Hungarian acatalasemia

Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) screening was used for searching mutations of the catalase gene in two Hungarian hypocatalasemic families. A syndrome-causing mutation was found in a PCR product containing exon 7 and its boundaries. Nucleotide sequence analyses detected a G to T substitution at position 5 of intron 7. The effect of this splice site mutation was confirmed by Western blot analyses demonstrating a decreased catalase protein level in these patients. These findings represent a novel type (C) of catalase mutations in the Hungarian acatalasemic/hypocatalasemic patients.

Hereditary catalase deficiencies and increased risk of diabetes

Partial or near-total lack of erythrocyte catalase activity is a rare condition, generally thought to be benign. However, little is known of the frequency of common diseases of adult onset in human beings with catalase deficiency. We report that, in a series of Hungarian patients with catalase deficiency, there is a higher frequency of diabetes than in unaffected first-degree relatives and the general Hungarian population. We speculate that quantitative deficiency of catalase might predispose to cumulative oxidant damage of pancreatic beta-cells and diabetes.

Anovel catalase mutation (a GA insertion) causes the Hungarian type of acatalasemia

Acatalasemia, a deficiency of enzyme catalase, is an autosomal recessive syndrome with an incidence of 5:106 in Hungary. We have examined the first Hungarian acatalasemic family for the disease-causing mutation. All exons of the catalase gene were screened by PCR-SSCP, PCR-heteroduplex, and nucleotide sequence analysis. The heteroduplex formation detected in exon 2 was verified by nucleotide sequence analysis. We found a GA insertion at nucleotide position 138, increasing the GA repeat number from 4 to 5. This GA insertion caused a frameshift in the amino acid sequence from position 68 to 133 and generated a TGA terminating codon at amino acid position 134. This truncated protein lacks the essential amino acid (histidine 74) in the active center. This finding can explain the decreased blood catalase activity in the Hungarian acatalasemic family.

Genetic heterogeneity of the 5' uncoding region of the catalase gene in Hungarian acatalasemic and hypocatalasemic subjects

The 5' uncoding region (165 bp), exon 1 (63 bp) and part of intron 1 (20 bp) of the catalase gene was amplified by PCR in acatalasemic (2), hypocatalasemic (19) patients and healthy individuals (10). The single strand conformational polymorphism of PCR products showed a highly polymorphic pattern. This polymorphism was supported by nucleotide sequence analyses yielding eight mutations. They are A to T, C to A and C to T at positions -21, -20, -18 of the 5' flanking region, T to C at positions 4, 44, 49 of the non-coding region and C to T and C to A at positions 12, 27 of exon 1. Of these nucleotide substitutions, the fourth, fifth, seventh and eighth are novel mutations. The mutations 1, 3, 6, 8 were present at least at heterozygous level in all acatalasemics and hypocatalasemics. None of these mutations may be the causal mutation(s) of acatalasemia as each of these nucleotide substitutions were detected in healthy subjects with normal blood catalase activity.

Further genetic heterogeneity in acatalasemia

A T-deletion at position 10 of exon 4 for catalase gene was reported as a novel mutation, causing a new genetic type of acatalasemia in Japan. This mutation, destroying a Hinf1 recognition site, was searched for in Hungarian acatalasemic (2) and hypocatalasemic (22) patients and in controls (27) by Hinf1 digestion and sequence analyses of a 203 bp polymerase chain reaction (PCR) product containing the entire exon 4. The Hinf1 polymorphism did not reveal any difference between controls and hypocatalasemic as well as acatalasemic patients. These results were confirmed by sequence analyses showing the T nucleotide for the two acatalasemic and for one unrelated hypocatalasemic patient, as well as for two controls. These findings represent further evidence that acatalasemia is heterogeneous at the DNA level.

Polymorphism of 5' of the catalase gene in Hungarian acatalasemia and hypocatalasemia

The amplified fragment length polymorphism of Hinf1 on the promoter region of the catalase gene in Hungarian acatalasemic and hypocatalasemic patients yielded three different patterns with five bands in total. The sequence analyses revealed A-to-T, C-to-A, and C-to-T mutations at positions -21, -20, and -18 upstream of the translational initiation site. The -21 A-to-T mutations were more frequent in acatalasemic and hypocatalasemic patients (36/2) than in controls (18/14). This mutation had been detected in Japanese acatalasemic patients while the other two are novel mutations. Two extra bands in the Hinf1 pattern are due to star-like activity that cleaved a G/ATTT sequence at position -4 to 0 upstream of the initiation site.

Reference ranges of normal blood catalase activity and levels in familial hypocatalasemia in Hungary

In 1756 healthy individuals the mean and S.D. values of blood catalase activity were 111.3 +/- 16.5 MU/l with lower blood catalase for females (107.7 +/- 14.4 MU/l, n = 880) than for males (117.9 +/- 16.8 MU/l, n = 876) while the ratios of blood catalase activity to blood hemoglobin concentration were not different (0.841 +/- 0.107 MU/g versus 0.849 +/- 0.119 MU/g). The decrease of blood catalase with age was greater in males (b = -0.084 MU/l year) than in females (b = -0.016 MU/l year). The screening of 3300 healthy citizens for hypocatalasemia yielded six families (0.18%), and three families were identified out of 1630 clinic patients. These nine families revealed 37 hypocatalasemic patients with 57.5 +/- 11.7 MU/l mean and S.D. of blood catalase activity. Similarly to the Japanese and the Hungarian actalasemic patients, the electrophoretic mobilities of catalase in erythrocytes of hypocatalasemic patients were indistinguishable from that of healthy controls.

Genetic heterogeneity in acatalasemia

203 bp long products containing exon 4 and its junctions from the catalase gene were generated by polymerase chain reaction (PCR). These products were analyzed by single strand conformational polymorphism (SSCP), hetero-duplex formation and nucleotide sequencing. No polymorphism was detected when the Hungarian acatalasemic sisters, their family members and normocatalasemic controls were analyzed. Sequence analyses did not show the G to A point mutation at position 5 of intron 4. This splicing mutation characterizes the Japanese-type of acatalasemia.

Hungarian hereditary acatalasemia and hypocatalasemia are not associated with chronic hemolysis

Two Hungarian acatalasemic and eight hypocatalasemic patients revealed normal erythropoesis. Contrary to their decreased defence system against the toxic hydrogen peroxide, the biochemical tests (serum catalase, serum hemoglobin, serum lactate dehydrogenase (LDH) ratio of LDH1 and LDH2 isoenzymes and serum haptoglobin) excluded hemolysis. The normal activity of glutathione peroxidase and the decreased catalase activity could prevent the lysis of the erythrocytes. In the presence of extremely high levels of hydrogen peroxide acute hemolysis may not be excluded; therefore, follow-up of these patients is required.

Further characterization of Hungarian acatalasemia by Hinf1 polymorphism of catalase gene

An Hinf1 associated restriction length polymorphism pattern is reported for the catalase gene of Hungarian normocatalasemic individuals and acatalasemic patients. The 2.4-kb pCAT 10 probe revealed 9 bands (2.1, 1.5, 1.2, 1.1, 0.9, 0.8, 0.6, 0.5 and 0.4 kb) with 9 distinct patterns for the controls. The same patterns were detected for the Hungarian acatalasemic patients. The examination of the A to T mutation of the Hungarian acatalasemic patients and their relatives at position -21 in the flanking region with Hinf1 polymorphism could not reveal any difference between the acatalasemic and the normocatalasemic catalase gene.

Characterization of acatalasemia detected in two Hungarian sisters

Acatalasemia was detected in 2 sisters of a Hungarian family. The pedigree of the family showed hypocatalasemia in the children of the patients and in 1 of their brothers, while the other members of the family had normal blood catalase activity. The biochemical characterization (catalase activity, electrophoretic migration, isoelectric point and enzyme stability) of the blood as well as tissue catalase of the acatalasemic patients yielded a catalase form which did not differ from normal.

Serum Catalase: Reversibly Formed Charge Isoform of Erythrocyte Catalase

The different electrophoretic mobilities of erythrocyte and serum catalase (EC 1.11.1.6) were confirmed and the causes responsible for their differences were examined. The presence of a catalase-binding protein in serum that could form a complex with erythrocyte catalase was excluded by incubating serum proteins with erythrocyte catalase. No new unequivocal catalase bands representing a catalase-binding protein were detected. The erythrocyte and serum catalase proved to be charge isoforms: their molecular masses, estimated by gel permeation chromatography or polyacrylamide gel electrophoresis in a nondenaturing system, were very similar, whereas their electrophoretic mobilities were different. Assay of serum catalase by gel permeation and hydrophobic chromatography yielded a product with the same electrophoretic mobility as that of erythrocyte catalase. Different dilution of erythrocyte catalase with human sera led to a gradual decrease of its mobility, 20-fold or greater dilution yielding the same results as for serum catalase. Similarly, when serum catalase was diluted 20-fold or more with 60 mmol/L phosphate buffer, it migrated similarly to erythrocyte catalase. I detected no effect of dialyzable serum ligands, NADPH, or protection of SH groups on the electrophoretic mobility of either catalase isoform. I conclude that formation of charge isoforms of catalase is caused by a reversible, conformational modification due to matrix effect of serum.

Serum catalase: reversibly formed charge isoform of erythrocyte catalase

The different electrophoretic mobilities of erythrocyte and serum catalase (EC 1.11.1.6) were confirmed and the causes responsible for their differences were examined. The presence of a catalase-binding protein in serum that could form a complex with erythrocyte catalase was excluded by incubating serum proteins with erythrocyte catalase. No new unequivocal catalase bands representing a catalase-binding protein were detected. The erythrocyte and serum catalase proved to be charge isoforms: their molecular masses, estimated by gel permeation chromatography or polyacrylamide gel electrophoresis in a nondenaturing system, were very similar, whereas their electrophoretic mobilities were different. Assay of serum catalase by gel permeation and hydrophobic chromatography yielded a product with the same electrophoretic mobility as that of erythrocyte catalase. Different dilution of erythrocyte catalase with human sera led to a gradual decrease of its mobility, 20-fold or greater dilution yielding the same results as for serum catalase. Similarly, when serum catalase was diluted 20-fold or more with 60 mmol/L phosphate buffer, it migrated similarly to erythrocyte catalase. I detected no effect of dialyzable serum ligands, NADPH, or protection of SH groups on the electrophoretic mobility of either catalase isoform. I conclude that formation of charge isoforms of catalase is caused by a reversible, conformational modification due to matrix effect of serum.

A simple method for determination of serum catalase activity and revision of reference range

A rapid, cost-efficient, spectrophotometric assay for serum catalase activity was developed. It was a combination of optimized enzymatic conditions and the spectrophotometric assay of hydrogen peroxide based on formation of its stable complex with ammonium molybdate. Lipemic and icteric sera increased the absorbance without influencing the catalase assay. Due to the high catalase activity in erythrocytes artificial hemolysis increased serum catalase activity. The imprecision of the method was CV less than 5.8% within run as well and day-to-day. The catalase assay performed using polarographic and spectrophotometric determination of hydrogen peroxide yielded a good correlation (r = 0.9602, b = 1.011, a = -0.648, n = 440). In 742 healthy individuals the mean and SD values of serum catalase were 50.5 +/- 18.1 kU/l with 17.7% higher activity in males than in females. Between 14-60 yr the serum catalase increased with age.

Origin of serum catalase activity in acute pancreatitis

Serum catalase activity was examined in 96 patients with the oedematous form and in 15 patients with the necrotic form of acute pancreatitis. Total catalase release into plasma was estimated to be 2,140 +/- 947 kU and 4,764 +/- 1,505 kU, respectively. The g equivalents of pancreas were 163 +/- 72 g and 362 +/- 133 g, being 2.03-fold and 4.52-fold higher than the whole mass of pancreas indicating the nonpancreatic origin of the total increase of serum catalase. In both types of acute pancreatitis serum haemoglobin, haematin, haptoglobin and LDH values supported the presence of haemolysis. The volumes of blood were 22.6 +/- 10.1 ml and 50.4 +/- 15.9 ml which are only 0.41% and 0.91% of the total blood volume. Taking these findings into account, in acute pancreatitis the major part of increase of serum catalase can be explained by its release from the erythrocytes.

Human erythrocyte catalase, isolation with an improved method, characterization and comparison to bovine liver catalase

Catalase enzyme was purified from human erythrocytes. The modified procedure of Mörikofer-Zwez et. al. [Eur. J. Biochem. 11: 49-57, 1969] yielded erythrocyte catalase with high specific activity and with one band on SDS polyacrylamide gel. Its other characteristics (isoelectric point; E405/280, E1%1cm at 280 nm and 405 nm) were in agreement with previously described findings. The results obtained for molecular mass, electrophoretic mobility, chromatographic behaviour on CM-Sepadex gel, addition test, and change of electrophoretic mobility in human serum showed differences between human erythrocyte catalase and bovine liver catalase. These results suggest that human erythrocyte catalase and bovine liver catalase are two distinct catalase forms.