[A study on antiprothrombin antibodies in antiphospholipid syndrome]

In this study we investigated the frequency and the type of manifestations of antiprothrombin antibodies (aFII) in patients with antiphospholipid syndrome (APS). In 16 (84.2%) of 19 patients with lupus anticoagulant (LA) and either anticardiolipin antibodies or antiphosphatidylserine antibodies, two types of abnormal patterns were shown on a crossed immuno-electrophoresis technique using anti-human prothrombin murine IgG. The slow-moving peak of prothrombin was detected in 8 patients, while a peak in the other patients had the slow-moving shoulder. These slow-moving materials might represent prothrombin-aFII complexes. In 13 patients who were studied on Western blots, IgGs of 11 patients (84. 6%) bound to human purified prothrombin, and the IgGs of 7 (53.8%) of these patients also bound to human purified alpha-thrombin. Our results indicate that aFII detected in patients with APS may explain part of the mechanism of LA.

Selective expression of the receptor tyrosine kinase, HTK, on human erythroid progenitor cells

HTK is a receptor tyrosine kinase of the Eph family. To characterize the involvement of HTK in hematopoiesis, we generated monoclonal antibodies against HTK and investigated its expression on human bone marrow cells. About 5% of the bone marrow cells were HTK+, which were also c-Kit+, CD34(low), and glycophorin A(-/low). Assays of progenitors showed that HTK+ c-Kit+ cells consisted exclusively of erythroid progenitors, whereas HTK- c-Kit+ cells contained progenitors of granulocytes and macrophages as well as those of erythroid cells. Most of the HTK+ erythroid progenitors were stem cell factor-dependent for proliferation, indicating that they represent mainly erythroid burst-forming units (BFU-E). During the erythroid differentiation of cultured peripheral CD34+ cells, HTK expression was upregulated on immature erythroid cells that corresponded to BFU-E and erythroid colony-forming units and downregulated on erythroblasts with high levels of glycophorin expression. These findings suggest that HTK is selectively expressed on the restricted stage of erythroid progenitors, particularly BFU-E, and that HTK is the first marker antigen that allows the purification of erythroid progenitors. Furthermore, HTKL, the ligand for HTK, was expressed in the bone marrow stromal cells. Our findings provide a novel regulatory system of erythropoiesis mediated by the HTKL-HTK signaling pathway.

Escherichia coli F1-ATPase subunit interactions: beta and gamma subunit peptides inhibit in vitro reconstitution of the active alpha beta gamma complex

For biochemical analysis of subunit interactions in the proton-translocating ATPase, a new approach with in vitro reconstitution of the Escherichia coli alpha beta gamma complex and the peptides derived from the subunits was established. Various portions of the beta or gamma subunits were used for in vitro reconstitution of the alpha beta gamma complex from the purified subunits. For the beta subunits, peptides corresponding to residues 226-459, 254-459, and 226-365 inhibited reconstitution, while those corresponding to residues 1-105, 1-146, and 295-459 did not. For the gamma subunits, peptides corresponding to residues 1-192 and 74-286 exhibited inhibitory effect on reconstitution, but the peptide containing residues 191-286 did not. Only inhibitory peptides blocked the assembly of the alpha beta gamma complex which was detected by nondenaturing polyacrylamide gel electrophoresis. These inhibitory peptides bound to the alpha or beta subunit on the filter, but the noninhibitory peptides did not. These results suggested that regions beta 254-294 and gamma 74-190 have sequences important for subunit interactions which interfered with those in the reconstitution mixtures. Based on comparison between X-ray crystallographic data of bovine alpha beta gamma complex and the present results, we discussed here the significance of the biochemical approach adopted in this study.

Does the presence of serum autoantibodies influence the responsiveness to interferon-alpha 2a treatment in chronic hepatitis C?

The serum autoantibodies, antinuclear antibody, anti-DNA antibody, anti-smooth muscle antibody, antithyroglobulin antibody, antimicrosomal antibody, antimitochondrial antibody, rheumatoid factor and antibody to deoxyribonucleoprotein were measured at the baseline and on completion of interferon-alpha 2a (IFN-alpha 2a) treatment in chronic hepatitis C (CHC) patients who did not present with any autoimmune disease prior to treatment. Of the 57 patients examined, 27 spontaneously manifested at least one autoantibody. Only the prevalence of rheumatoid factor (26%) was significantly higher in the CHC patients than in the control subjects. There were no differences in the prevalence of the 8 autoantibodies examined between hepatitis C virus (HCV) genotypes 1b and 2a/2b. Twenty-six patients responded to IFN-alpha 2a. Subclinical hypothyroidism developed in two patients with elevated antithyroid antibody titres during treatment. No relationship was observed between changes in the status of autoantibodies and either response to IFN-alpha 2a or HCV genotype. Irrespective of the HCV genotype, autoantibodies might be present in CHC patients before and during the IFN-alpha 2a treatment. The presence of such antibodies does not represent a contraindication to the use of IFN-alpha 2a in CHC patients not complicated by autoimmune diseases. Careful observations are necessary for CHC patients positive for antithyroid antibodies during the IFN-alpha 2a treatment. Preexisting or newly developed autoantibodies do not necessarily predict a poor response to IFN-alpha 2a.

Protection by alpha2-macroglobulin of tissue plasminogen activator against inhibition by plasminogen activator inhibitor-1

Tissue plasminogen activator (tPA) is widely used in the treatment of acute myocardial infarction (MI). However, its thrombolytic efficacy does not correlate with the dose administered. The interactions between tPA, alpha2-macroglobulin (alpha2-M), and plasminogen activator inhibitor-1 (PAI-1) were investigated both in vitro and in patients undergoing tPA therapy for MI in an attempt to identify variables that might affect the clinical efficacy of tPA. Purified alpha2-M (5.4 mg/ml) protected 16.0% or 22.4% of tPA (12.5 IU/ml) activity from inhibition by PAI-1 at 4 or 8 IU/ml in vitro. Of nine patients treated with 5-20 mega IU of tPA for MI, the plasma activity of tPA remained increased for 15-30 min after the cessation of infusion in eight; the patient who failed to exhibit a persistent increase in tPA activity had a low plasma concentration of alpha2-M. Total tPA activity, derived from the area under the activity-versus-time curve (AUC), showed a significant inverse correlation with the ratio of the plasma PAI-1 activity to the plasma alpha2-M concentration. Total tPA activity did not correlate with plasma PAI-1 activity or plasma alpha2-M concentration alone. Results suggest that alpha2-M, by binding to tPA, protects the latter against inhibition by PAI-1.

[Leukocytapheresis for ulcerative colitis]

Major inclusion criteria for leukocytapheresis (LCAP) therapy were mainly insufficient response to conventional drugs therapy. LCAP was administered once a week for 5 weeks of intensive therapy and once approximately a month for maintenance therapy, for 38 patients with UC. LCAP could remove approximately 1 x 10(10) white blood cells in each session. In the evaluation, we classified the response to the LCAP as: 1) excellent, 2) moderately improved, 3) no change, and 4) deterioration. Clinical improvement was recognized in 29 of 38 patients (76%) including 8 with dramatic response during the intensive therapy, and continued throughout the maintenance therapy in 26 patients (68.4%). Even though their symptoms were mild, the patients with more than 5 years UC history seemed to be not effective. The patients with moderately improvement and with excellent response have kept remission for about 20 months and about 2.5 years on an average, respectively. Clinical and blood examinations showed no side effects in any cases. It suggests that LCAP is able to be a UC treatment between drug therapies and an operation.

[Remission by leukocytapheresis for a patient with ulcerative colitis found refractory by conventional drug therapies]

A 40-year-old male was admitted to our hospital on August 30, 1994 to receive a new ulcerative colitis (UC) therapy, leukocytapheresis (LCAP). On the admission day, he had bloody stool 5 to 6 times/day, abdominal pain, slight fever, and hypoproteinemia. His UC type was moderately severe left-sided colitis with pseudopolyposis. Prior to admission to our hospital, his condition had not improved for about 9 months, despite drug therapies such as salicylazosulphapyridine, intravenous high dose prednisolone, protease inhibitor, intraarterial hydrocortisone sodium succinate, 4 series of pulse therapies with metylpredonisolone, enema of corticosteroid, azathioprine (Imuran), and cyclosporine at another hospital. Thus he was introduced to our college hospital and treated by LCAP since September 1. After 10 LCAP sessions, remission was observed and the patient discharged on December 23. Until he was later operated on for heavy bleeding after he had discontinued treatment and had drunk heavily, he had maintained remission for 13 months with LCAP only once a month even after we gradually decreased the other medical supports and stopped all of them. After LCAP, the normalization of high percentage of leukocytes presented HLADR+ and lymphocytes presented CD 11 a+ CD 8+ was also observed. This suggests LCAP intercepts the excess immune reaction in UC by removing leukocytes.

The expression of murine cutaneous late phase reaction requires both IgE antibodies and CD4 T cells

BACKGROUND

Exposure of atopic patients to a specific allergen evokes an immediate response which is followed, in many cases, by a late phase reaction (LPR) some hours later. Here we have examined the immunological mechanisms required for the expression of cutaneous LPR in mice.

METHODS

BALB/c mice were immunized by i.p. injection of ovalbumin (OVA) and alum actively or by i.v. injection of anti-OVA IgE monoclonal antibody (mAb) passively. After challenge by intradermal injection of OVA into ears, the changes in ear thickness, the number of eosinophils, and the levels of IL-4 and IFN-gamma protein at the site of antigen challenge were examined.

RESULTS

Actively immunized mice developed a biphasic response at the site of OVA injection, while mice passively immunized with IgE anti-OVA mAb displayed a strong early response but no LPR. Cell transfer experiments using BALB/c nu/nu mice revealed that both OVA-specific IgE mAb and OVA-primed CD4 T cells were required to evoke LPR. Moreover, LPR was associated with increased levels of IL-4 production concomitant with reduced IFN-gamma production and was abolished by pretreatment with anti-IL-4 neutralizing mAb.

CONCLUSION

It is suggested that murine cutaneous LPR against OVA is a type 2 inflammatory response in which both IgE antibodies and CD4 T cells play an obligatory role.

A rapid nylon-fiber syringe system to deplete CD14+ cells for positive selection of human blood CD34+ cells. Use of immunomagnetic microspheres

To achieve a rapid and an efficient purification of CD34+ cells, we devised a nylon-fiber syringe (NF-S) and we manipulated it to deplete adherent cells from normal human blood mononuclear cells (MN cells). The cells processed by NF-S were further purified as the CD34+ fraction, using CD34 monoclonal antibody, immunomagnetic microspheres and chymopapain treatment to detach the microspheres. When steady-state human peripheral blood MN cells were processed by NF-S at 24 degrees C for 5 min, the frequency of monocytes (CD14+ cells) significantly decreased from 22.0 +/- 5.2% to 2.5 +/- 0.4%, with a 73% recovery of CD34+ cells. The subsequent immunomagnetic positive selection achieved preparations of 91 +/- 8% pure CD34+ cells with a 86 +/- 23% yield. The overall yield of CD34+ cells was 44 +/- 11%, and the time required for all procedures was 5 h. There was a tight and an inverse correlation (P < 0.0001) between the frequency of CD14+ cells in the initial cell population and the purity of CD34+ cells in the final preparation. A recommended frequency of CD14+ cells for achieving preparations of over 90% pure CD34+ cells was less than 4.4%. When combining NF-S and immunomagnetic microspheres, efficient bench-top separation of CD34+ cells in steady-state peripheral blood can be done in any laboratory, and fluorescence-activated cell-sorting is not required.

Application of a colon delivery capsule to 5-aminosalicylic acid and evaluation of the pharmacokinetic profile after oral administration to beagle dogs

Pressure-controlled colon delivery capsule (PCC) containing 5-aminosalicylic acid (5-ASA) for the treatment of inflammatory bowel disease (IBD) was prepared and evaluated by an in vivo experiment using beagle dogs. As a reference drug, sulfasalazine (SASP), prodrug of 5-ASA, was used as a plain gelatin capsule preparation. After the oral administration of SASP at the does of 25.0 mg/kg, the mean time when the plasma 5-ASA concentration reaches to its maximum (Tmax) was 9.0 hr. In the case of 5-ASA administered in PCC, at the doses of 12.5 and 25.0 mg/kg, Tmaxs were 5.3 and 5.3 hr, respectively. Although the time for the first appearance of 5-ASA into the systemic circulation was almost the same value between SASP capsule and PCC containing 5-ASA, longer Tmax was observed from SASP capsule than from PCC. These results suggest that this 5-ASA preparation would be an useful dosage form for the therapy of IBD from the point of avoiding the side effect of sulfapyridine, one of the metabolites of SASP.

Structural comparisons of cell organelles and nuclei in rat hepatocytes with three different fixation techniques

The morphological properties of cell organelles and nuclei in rat hepatocytes were compared, when the hepatocytes were either chemically fixed in glutaraldehyde and osmium (GA-Os), chemically fixed only in osmium (Os-2h) or physically fixed with a microwave-irradiated osmium (Mw-Os) fixative for a short duration. Judging from the fine structure, the mitochondria and rER were best preserved after physical fixation; because of the smooth surfaces and regular open contours, but both organelles shrank in the two chemical fixatives. The Golgi complexes and peroxisomes of the hepatocytes were not markedly changed by any of the fixative procedures. However the lysosomes and sER were changed to some extent after physical fixation. In the nucleus, the two kinds of chromatins and the nucleolus were best preserved with physical fixation. In conclusion, physical fixation is a very simple and fast procedure that is convenient for routine electron microscopy if some attention is paid to the morphological changes.

Role of cytokines in leukemic type growth of myelodysplastic CD34+ cells

The clonal growth of progenitor cells from myelodysplastic syndromes (MDS) can be subdivided into four growth patterns: (1) normal, (2) no growth or low plating efficiency, (3) low colony and high cluster number, and (4) normal or high colony number with a large number of clusters. The former two (1 and 2) can be referred to as nonleukemic patterns and latter two (3 and 4) as leukemic. In a search for a role for cytokines in leukemic-type growth of MDS progenitor cells, marrow CD34+ cells were purified up to 94% for 8 normal individuals and 88% for 12 MDS patients, using monoclonal antibodies and immunomagnetic microspheres (MDS CD34+ cells). The purified CD34+ cells were cultured for 14 days with various combinations of cytokines, including recombinant human macrophage colony-stimulating factor (rM-CSF), granulocyte-CSF (rG-CSF), granulocyte-macrophage-CSF (rGM-CSF), interleukin-3 (rIL-3), and stem cell factor (SCF; a ligand for c-kit) in serum-free medium. The clonal growth of MDS CD34+ cells supported by a combination of all of the above cytokines was subdivided into the two patterns of leukemic or nonleukemic, and then the role of individual or combined cytokines in proliferation and differentiation of MDS CD34+ cells was analyzed in each group. Evidence we obtained showed that SCF plays a central role in the leukemic-type growth of MDS CD34+ cells and that G-CSF, GM-CSF; and/or IL-3 synergize with SCF to increase undifferentiated blast cell colonies and clusters over that seen in normal CD34+ cells. SCF is present in either normal or MDS plasma at a level of nanograms per milliliter, and this physiologic concentration of SCF can stimulate progenitor cells. This means that progenitor cells are continuously exposed to stimulation by SCF in vivo and that MDS leukemic cells have a growth advantage over normal blast cells. This depends, at least in part, on cytokines such as G-CSF, GM-CSF, IL-3, and SCF.

Lipopolysaccharides selectively inhibit mouse placental lactogen-II secretion through stimulation of interleukin-1 alpha (IL-1 alpha) and IL-6 production

To determine whether lipopolysaccharides (LPS) regulate mouse placental lactogen-I (mPL-I), mPL-II, and mouse GHRF (mGHRF) secretion, mouse placental tissue from days 7, 9, and 12 of pregnancy was dispersed with collagenase and the purified trophoblast cells were cultured in a serum-free medium with or without LPS for 5 days. LPS significantly inhibited mPL-II secretion by cells from days 9 and 12 of pregnancy. However, LPS did not affect mPL-II secretion by cells from day 7 of pregnancy, mPL-I secretion by cells from days 7 and 9 of pregnancy, or mGHRF secretion by cells from day 12 of pregnancy. The inhibitory effect of LPS on mPL-II secretion by cells from day 12 of pregnancy was dose-dependent. Steady-state levels of mPL-II mRNA were significantly reduced by incubation of placental cells from day 12 of pregnancy with LPS. The inhibitory effect of LPS on mPL-II secretion was abolished by the addition of antibodies to IL-1 alpha and IL-6. These findings suggest that LPS selectively inhibit mPL-II secretion, at least partly through increases in IL-1 and IL-6 production, after midpregnancy.

Proliferation and differentiation of myelodysplastic CD34+ cells

Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders of hematopoiesis involving hyperproliferative and ineffective hematopoiesis associated with morphologic evidence of marrow cell dysplasia resulting in refractory cytopenia(s), and an increased risk of transformation into acute myeloblastic leukemia (AML). The administration of colony-stimulating factor(s) (CSFs) to patients with MDS increased blood neutrophil concentrations, in most patients, and was also expected to be beneficial and to prevent infections. However, the progression to AML during the treatment with CSFs was suspected in some patients. Therefore, extensive in vitro studies were expected to lead to the establishment of criteria for selection of patients who are likely to benefit from CSF's as well as to establish the overall value of the different types of CSFs therapy. For this purpose, in vitro colony assays provide an excellent tool for investigating the biologic characteristics of MDS progenitor cells. However, conditions of the culture must be such that each progenitor can express its full potential for proliferation and differentiation. Because of the above, MDS progenitor cells cannot be used because they carry an impairment in proliferation and differentiation. To address this problem, one needs to know how many cells are being handled and the maximum numbers of colonies and clusters expected. CD34, a stem cell phenotype, is at present one of the best markers of progenitor cells, and can be used for purposes of purification. Using a defined number of CD34+ cells, it was feasible to make direct investigations on MDS progenitor cells. In this review the properties of MDS progenitor cells are described, in association with proliferation and differentiation, with special emphasis on the phenotypic subpopulations of MDS CD34+ cells.

Characterization of terminally differentiated cell state by categorizing cDNA clones derived from chicken lens fibers

To characterize a terminally differentiated state of cells at the gene expression level, a cDNA library of chicken lens fibers was analyzed. The major population of the library consisted of cDNAs encoding delta-crystallin (about 35% of the recombinants) and other crystallins (alpha A-, alpha B-, beta A3/A1-, beta B1-, beta B2-), as well as cytoskeletal proteins (CP49, CP95), and membrane protein (MP28). These cDNA clones representing lens structural proteins known, accounted for about 60% of the library. When 96 clones were randomly selected from this library, 55 clones corresponded to the above-mentioned major class proteins. Analyses of the remaining clones indicated that many of them were expressed in a lens-specific manner at very low levels. The partial nucleotide sequence analysis of these clones revealed that two cDNAs corresponded to the genes encoding lens-type connexin, three cDNAs to the genes encoding housekeeping proteins, and some cDNAs to the genes encoding regulatory proteins. The mRNA composition in the chicken lens fiber cells indicated rather simple organization of mRNA species of this cell type, and gave scope to the possibility of full description of differentiated lens fiber cells at gene activity level.

Interactions of the F1-ATPase subunits from Escherichia coli detected by the yeast two-hybrid system

Subunit interactions among the F1-ATPase subunits were studied by the yeast two-hybrid system. Various pairwise combinations of genes encoding alpha, beta, gamma, delta and epsilon subunits of Escherichia coli H+-ATPase fused to the DNA-binding or activation domain of the yeast GAL4 gene were introduced into yeast and expression of a reporter gene encoding beta-galactosidase was detected. Combinations of the alpha and beta subunit genes, and of the epsilon and gamma subunit genes showed high levels of reporter gene expression, while those of alpha and delta, beta and delta, gamma and delta, and delta and epsilon demonstrated weak but significant reporter gene expression. However, combinations of alpha and gamma, beta and gamma, alpha and epsilon, and beta and epsilon did not induce reporter expression. None of the fused genes alone induced reporter gene expression. These results suggested that specific and strong interactions between the alpha and beta, gamma and epsilon, and weak interactions between the alpha and delta, beta and delta, and gamma and delta subunits occurred in yeast cells in the two-hybrid system. Effects of previously identified mutant beta subunits with Leu-40 to Pro. Glu-41 to Lys or Pro-332 to Gln substitutions which caused defects in molecular assembly of F1-ATPase were analyzed with regard to alpha-beta interactions. No interaction of the alpha and beta subunits was observed in this system using the beta subunit with mutation of Pro-332 to Gln. However, for the other two mutations, alpha-beta interactions were observed. This system may be useful for isolating mutants which have defects in interaction of F1-ATPase subunits.

Point mutation in the alpha-galactosidase A gene of atypical Fabry disease with only nephropathy

A point mutation in exon 6 of the alpha-galactosidase A gene (alpha-GAL A) was found in a Japanese hemizygous male without typical manifestations of Fabry disease other than renal involvement. This 45-year-old man developed moderate proteinuria and was diagnosed with Fabry disease on the basis of renal histologic findings and prominent decreases in alpha-GAL A activity in his plasma, urine, leukocytes, and skin fibroblasts. Determination of the cDNA sequence of his alpha-GAL A gene revealed substitution of a G to A in codon 301, resulting in a glutamine rather than an arginine residue. Our case is unique in that this patient only demonstrated renal manifestations while all other reported patients with atypical Fabry disease, including a case with the identical point mutation, present with a cardiomyopathy. Direct DNA sequencing of exon 6 and measurement of alpha-GAL A activity among the patient's family confirmed that the mutation was transmitted from his mother.

Mobilization of peripheral blood progenitor cells following CHOP treatment combined with delayed granulocyte colony-stimulating factor administration in patients with non-Hodgkin's lymphoma

The kinetic change in peripheral blood progenitor cells (PBPC) during 3 to 6 cycles of standard CHOP regimen supported with human recombinant granulocyte colony-stimulating factor (rG-CSF) was investigated in three patients with newly diagnosed intermediate grade, diffuse large cell type, non-Hodgkin's lymphoma (NHL) without bone marrow invasion. Patients were given rG-CSF subcutaneously (2 mu g/kg/day) initiated when total leukocytes was < 3.0 x 10(9)/1. When the leukocyte count remained at >3.0 x 10(9)/1, rG-CSF was started 10 days following the prior CHOP. Treatment with rG-CSF was discontinued after the leukocyte count reached >10.0 x 10(9)/1, and CHOP was started the next day (CHOP-G regimen). The number of PBPC was monitored by clonal assay in patients 1-3. No severe leukopenia with <0.5 x 10(9)/1 of neutrophils was seen in any patient. Colony-forming unit granulocyte-macrophage (CFU-GM) significantly increased after 2-3 days of consecutive administration of rG-CSF. The magnitudes of maximum amplification of CFU-GM in patients 1, 2, and 3, were 56-fold (during 3 cycles of CHOP-G), 216-fold (during 2 cycles), and 67-fold (during 4 cycles), respectively, and the absolute numbers of the maximum CFU-GM/ml blood were 983, 7,568, 9,865, respectively. In one patient who was given 6 cycles of CHOP-G, the peak values of mobilized CFU-GM in each cycle did not substantially decrease until 6 cycles of CHOP-G had been completed. Thus, the CHOP-G regimen described here seems to be very efficient increasing the circulating CFU-GM prior to harvesting PBPC.

Four polymorphs of a cobaloxime complex with different solid-state photoisomerization rates

The complex (2-cyanoethyl)bis(dimethylglyoximato)(triphenylphosphine)cobalt(III), [Co(C4H7N2O2)2(C3H4N){P(C6H5)3}], when it was crystallized rapidly from an aqueous methanol solution, has four crystal forms, three of which were obtained separately from different solvents in large amounts. The crystal structures of the four forms were determined by X-rays. The molecular structures in the four forms have different conformations around the Co—C and Co—P bonds. The packing energy calculation indicated that the four forms have approximately the same energy. The 2-cyanoethyl group of this complex was isomerized to the 1-cyanoethyl group when the powdered sample of the complex was irradiated with a xenon lamp. For three crystal forms prepared separately, the solid-state photoisomerization rates were measured from the change in the IR spectra, assuming first-order kinetics. A quantitative relationship between the rate constant and the size of the reaction cavity for the 2-cyanoethyl group has been obtained for the three crystal forms.

Separation of functional domains for the alpha-1,4 and alpha-1,6 hydrolytic activities of a Bacillus amylopullulanase by limited proteolysis with papain

An amylopullulanase (APase) from alkalophilic Bacillus sp. KSM-1378 hydrolyzes both alpha-1,6 linkages in pullulan and alpha-1,4 linkages in other polysaccharides, each maximally active at an alkaline pH, to generate oligosaccharides. We analyzed proteolytic fragments that were produced by exposing pure APase to various proteases, to identify its catalytic domain(s). The intact, pure 210-kDa APase was partially digested with papain for a short time, yielding simultaneously two smaller non-overlapping active fragments, designated amylose-hydrolyzing fragment (AHF114, 114 kDa) and pullulan-hydrolyzing fragment (PHF102, 102 kda). The two truncated protein fragments, each containing a single catalytic domain, were purified to homogeneity. The purified AHF114 and PHF102 had similar enzymatic properties to the amylase and pullulanase activities, respectively, of intact APase. The partial amino-terminal sequences of APase and AHF114 were both Glu-Thr-Gly-Asp-Lys-Arg-Ile-Glu-Phe-Ser-Tyr-Glu-Arg-Pro and that of PHF102 was Thr-Val-Pro-Leu-Ala-Leu-Val-Ser-Gly-Glu-Val-Leu-Ser-Asp-Lsy-Leu. These results were direct evidence that the alpha-1,6 and alpha-1,4 hydrolytic activities were associated with two different active sites in this novel enzyme. Our alkaline APase is obviously a "biheaded enzyme".