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Biomedical subjects

K Soda

Publications and source records attributed to K Soda.

At least 163 records · Page 9Linked to original sources
PubMed1993

[Prevalence of hepatitis C virus and human immunodeficiency virus infection among Japanese female prostitutes].

To investigate the incidence of hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infection in Japanese sexual workers, 191 out of 194 female prostitutes working in a certain district of the Tokyo metropolitan area were tested for anti-HCV, anti-hepatitis B virus (HBV), anti-HIV and anti-Treponema pallidum (TP). They were also interviewed with regard to their past history of blood transfusion, vaccination against HBV, liver diseases and repeated skin piercing treatments such as tattooing, acupuncture and intravenous drug use. Sera from 300 female blood donors (aged 20 s-40 s), of the same district, collected during the same year, were assessed for comparison. Incidence of seropositives for anti-HCV and anti-TP were found to be significantly high in the prostitute group (11.0% and 16.2%, respectively) compared to the control (0% for both). Anti-HBV seropositives were 14.1% in the prostitute group and 12.7% in the control group without significant difference and none of our subjects were found to be anti-HIV positive. Among HCV infected only 5 experienced repeated skin-piercing treatment and none underwent blood transfusion. From these results it is concluded that HCV has a potential for being transmitted by heterosexual contact, although the exact risk for infection needs to be determined by further investigation.

Adult↗
PubMed1993

[The correlation between changes in EEG and eye movement (EOG) accompanied by lowered arousal level].

We investigated the correlation between the components of spontaneous eye movement (EOG) and EEG in six healthy individuals. The study was conducted in three periods; from the resting to drowsy stage, from the drowsy to spontaneous awakening stage, and in the forced waking stage. EEG, as registered from bipolar electrodes attached between the left parietal region (P3) and the left occipital region (O1), was monitored continuously by the FFT method with a segment of 12.8 seconds. Rapid eye movement and slow eye movement were observed simultaneously. In conclusion, even when the arousal level varies considerably, there is a close correlation between frequency of rapid eye movement and EEG patterns of 10.16 integral of 10.94 Hz & 17.97 integral of 19.53 Hz (simple correlation p < 0.01). Additionally, during the forced waking period (after stage 2), delta and theta bands increased in cases along with sleepiness. Even if the depth of sleep was the same, one's mood upon awakening was determined by the frequency of slow waves before awakening.

Adult↗
PubMed1993

[Evaluation of lidocaine metabolite (monoethylglycinexylidide) as a liver function test].

In order to determine whether or not the lidocaine metabolism, monoethylglycinexylidide (MEGX) formation, could be used as a liver function test, we measured the serum levels of MEGX in 38 patients. There were significant correlations between values of MEGX (MEGX15, MEGX30, AUC15-30, AUC0-180) and conventional liver function tests (ICG R15, AT III, T. Bil). It appeared that value of MEGX 30 had maximum factor loading on conventional liver function tests by using principal component analysis. The advantage of adapting the MEGX formation as a liver function test of drug metabolism is simplicity of the method. MEGX formation could be useful index of the total liver function.

Evaluation Studies as Topic↗
PubMed1992

Partial reactions of bacterial D-amino acid transaminase with asparagine substituted for the lysine that binds coenzyme pyridoxal 5'-phosphate.

In bacterial D-amino acid transaminase (EC 2.6.1.21) replacement of Lys-145, which is covalently linked to the coenzyme pyridoxal 5'-phosphate in the wild-type enzyme, by an Asn residue gave a mutant enzyme (K145N) that slowly performed each half-reaction, as determined by spectral measurements. With the wild-type enzyme, the kinetics of these events were so rapid that pre-steady-state conditions were needed for their determination. The internal aldimine between coenzyme and Lys-145 was rapidly reduced with NaCNBH3 in the wild-type enzyme, whereas in the mutant enzyme the coenzyme, which is not covalently linked to the protein, was more resistant to reduction; the reduced forms of both wild-type and mutant enzymes were inactive. With large amounts of the K145N mutant enzyme and either amino acid or keto acid substrate alone, the formation of some reaction intermediates, i.e., the external aldimine with D-alanine and the ketimine with alpha-ketoglutarate, can be measured by conventional spectroscopy. Suicide substrates also induced slow spectral shifts of the E-PLP form of the enzyme. For the K145N enzyme, exogenous amines affected only the rate of the transaldimination but not the removal of the alpha-proton of the substrate. These results suggest that in the mutant enzyme some amino acid side chain other than Lys-145 performs this function. In order to identify this site, the K145N mutant enzyme was completely inactivated by the radiolabeled suicide substrate D-serine. Peptide mapping of tryptic digests showed that Lys-267 was the modified site.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗
PubMed1992

Properties of aspartate racemase, a pyridoxal 5'-phosphate-independent amino acid racemase.

Aspartate racemase from Streptococcus thermophilus contains no pyridoxal 5'-phosphate or other cofactors such as FAD, NAD+, and metal ions. It was affected by neither carbonyl reagents such as hydroxylamine nor sodium borohydride but was strongly inhibited by iodoacetamide and other thiol reagents. Aspartate, cysteate, and cysteine sulfinate were the only substrates. The Km values for L- and D-aspartate were 35 and 8.7 mM, respectively. The enzyme catalyzed the exchange of alpha-hydrogen of the substrate with the solvent hydrogen. Racemization of L-aspartate in 2H2O showed an overshooting in the optical rotation of aspartate before the substrate was fully racemized. This shows that the removal of alpha-hydrogen of the substrate is at least partially rate-determining. When L- or D-aspartate was incubated with aspartate racemase in tritiated water, tritium was incorporated preferentially into the product enantiomer. The results strongly suggest that aspartate racemase contains two hydrogen acceptors.

Amino Acid Isomerases↗
PubMed1992

Inactivation of dimeric D-amino acid transaminase by a normal substrate through formation of an unproductive coenzyme adduct in one subunit.

D-amino acid transaminase, which contains pyridoxal 5'-phosphate (vitamin B6) as coenzyme, catalyzes the formation of D-alanine and D-glutamate from their corresponding alpha-keto acids; these D-amino acids are required for bacterial cell wall biosynthesis. Under conditions usually used for kinetic assay of enzyme activity, i.e., short incubation times with dilute enzyme concentrations, D-alanine behaves as one of the best substrates. However, the enzyme slowly loses activity over a period of hours when exposed to substrates, intermediates, and products at equilibrium. The rate of inactivation is dependent on enzyme concentration but independent of substrate concentration greater than Km values. Continuous removal of the product pyruvate by enzymic reduction precludes the establishment of equilibrium and prevents inactivation. The formation of small but detectable amounts of a quinonoid intermediate absorbing at 493 nm is proportional to inactivation. Studies with [14C]-D-alanine labeled on different carbon atoms indicate that the alpha-carboxyl group of the substrate is absent in the inactive enzyme; such decarboxylation is not a usual function of this enzyme. The inactive transaminase contains 1.1 mol of [14C]-D-alanine-derived adduct per mole of dimeric enzyme; this finding is consistent with the 50% reduction in the fluorescence intensity at 390 nm (due to the PMP form of the coenzyme) for the inactive enzyme. Thus, inactivation of one subunit of the dimeric enzyme renders the entire molecule inactive. Inactivation may occur when a coenzyme intermediate, perhaps the ketimine, is slowly decarboxylated and then undergoes a conformational change from its catalytically competent location.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗
PubMed1992

Reaction mechanism of glutamate racemase, a pyridoxal phosphate-independent amino acid racemase.

Glutamate racemase of Pediococcus pentosaceus contained no cofactor, and was completely inactivated by a thiol reagent. The role of a cysteine residue in the enzyme reaction was studied by chemical modification. The modification of this cysteine residue resulted in a concomitant loss of activity. DL-Glutamate protected the enzyme from inactivation. The inactivated enzyme was reactivated by addition of dithiothreitol. The racemization in 2H2O showed an overshoot in the optical rotation of glutamate before the substrate was completely racemized. This indicates that the removal of alpha-hydrogen is the rate determining step. During the racemization of D- or L-glutamate in 3H2O, tritium was incorporated preferentially into the product. Glutamate is racemized by the enzyme probably through a two base mechanism.

Amino Acid Isomerases↗
PubMed1992

Leucine dehydrogenase from Bacillus stearothermophilus: identification of active-site lysine by modification with pyridoxal phosphate.

We have constructed an efficient expression plasmid for the leucine dehydrogenase gene previously cloned from Bacillus stearothermophilus. The recombinant enzyme was overproduced in Escherichia coli cells to a level of more than 30% of the total soluble protein upon induction with isopropyl beta-D-thiogalactopyranoside. The enzyme could be readily purified to homogeneity by heat treatment and a single step of ion-exchange chromatography. The purified enzyme was inactivated in a time-dependent manner upon incubation with pyridoxal 5'-phosphate (PLP) followed by reduction with sodium borohydride. The inactivation was completely prevented in the copresence of L-leucine and NAD+. Concomitantly with the inactivation, several molecules of PLP were incorporated into each subunit of the hexameric enzyme. Sequence analysis of the fluorescent peptides isolated from a proteolytic digest of the modified protein revealed that Lys80, Lys91, Lys206, and Lys265 were labeled. Among these residues, Lys80 was predominantly labeled and, in the presence of L-leucine and NAD+, was specifically protected from the labeling. Furthermore, a linear relationship of about 1:1 was observed between the extent of inactivation and the amount of PLP incorporated into Lys80. A slightly active mutant enzyme, in which Lys80 is replaced by Ala, was not inactivated at all by incubation with PLP, showing that the inactivation is correlated with the labeling of only Lys80. Lys80is conserved in the corresponding regions of all the amino acid dehydrogenase sequences reported to date. These results suggest that Lys80 is located at the active site and plays an important role in the catalytic function of leucine dehydrogenase.

Amino Acid Oxidoreductases↗
PubMed1992

[Case report: chronic aggressive pulmonary sarcoidosis with bilateral cavitation].

A 34-year-old male patient was admitted to our hospital because of progressive exertional dyspnea and weight loss (8 kg in one year). Twelve years previously, he had had an episode of uveitis accompanied with bilateral hilar lymphadenopathy. Scalene node biopsy at that time revealed non-caseating epithelioid granulomas. Four years later, a follow-up chest radiograph showed bilateral fine nodular lesions. The bilateral parenchymal lesions gradually increased in density, and eventually, formed a confluent air-space consolidation containing multi-ocular cavities. On physical examination, the patient was emaciated (Ht 165 cm, Wt 40 kg). Nodular cutaneous lesions were present on his face and elbows. Hypoxemia with hypercapnea (PaO2 56 Torr, PaCO2 51 Torr) was noted. Repeated sputum cultures yielded negative results for acid-fast bacilli, fungi, and other pathological organisms. A transbronchial lung biopsy specimen obtained from near the cavitary lesion revealed non-caseating granulomas compatible with sarcoidosis. Skin lesion biopsy showed similar findings. The cavitation, was therefore considered to be due to ischemic necrosis of confluent sarcoid granulomas. Prednisolone (40 mg daily) was given with a prompt improvement of symptoms including dyspnea, as well as the radiographic abnormalities. We conclude that uncomplicated pulmonary sarcoidosis may rarely develop into an aggressive parenchymal disease with cavitation. It is of importance to differentiate such cases from infectious diseases (tuberculosis, mycosis etc.) because of the need for corticosteroid treatment.

Adult↗
PubMed1992

[Clinical study of bronchial inhalation challenge in summer-type hypersensitivity pneumonitis induced by Trichosporon cutaneum].

To evaluate the methods and criteria of judgement for the bronchial antigen inhalation challenge test, the test was performed with culture filtrate antigen of serotype I and II of Trichosporon cutaneum in 18 patients with summer-type hypersensitivity pneumonitis from 15 families. The quantity of 15 mg of culture filtrate antigen was adequate, and had no side effects. In the tests, 17 of 18 patients showed a positive reaction to both or either, serotype of antigen. In 36 performances of inhalation, there were 21 positive reactions and 15 negative reactions. According to the criteria of judgment for inhalation challenge test, the positive response rates of observation items were 75% for symptoms and signs, and 51% for laboratory data. Items with a high positive rate were cough, crepitant rales, and decrease of PaO2. On the other hand, low positive rates were observed for decrease of DLco, VC and positive CRP. Items with both high sensitivity and high specificity were cough, crepitant rales and decrease of PaO2. The low positive rate of decreased DLco was due to insufficient improvement before inhalation challenge. It was concluded that our methods and criteria of judgment for bronchial inhalation challenge test are useful.

Adolescent↗
PubMed1991

Thermostable alanine racemase of Bacillus stearothermophilus. Construction and expression of active fragmentary enzyme.

Limited proteolysis studies on alanine racemase suggested that the enzyme subunit is composed of two domains (Galakatos, N. G., and Walsh, C. T. (1987) Biochemistry 26, 8475-8480). We have constructed a mutant gene that tandemly encodes the two polypeptides of the Bacillus stearothermophilus enzyme subunit cleaved at the position corresponding to the predicted hinge region. The mutant gene product purified was shown to be composed of two sets of the two polypeptide fragments and was immunologically identical to the wild-type enzyme. The mutant enzyme, i.e. the fragmentary alanine racemase, was active in both directions of the racemization of alanine. The maximum velocity (Vmax) was about half that of the wild-type enzyme, and the Km value was about double. Absorption and circular dichroism spectra of the fragmentary enzyme were similar to those of the wild-type enzyme. An attempt was made to separately express in Escherichia coli a single polypeptide corresponding to each domain, but no protein reactive with the antibody against the wild-type alanine racemase was produced. Therefore, it is suggested that the two polypeptide fragments can fold into an active structure only when they are co-translated and that they correspond to structural folding units in the parental polypeptide chain.

Alanine Racemase↗
PubMed1991

Effect of substitution of a lysyl residue that binds pyridoxal phosphate in thermostable D-amino acid aminotransferase by arginine and alanine.

Lys-145 of the thermostable D-amino acid aminotransferase, which binds pyridoxal phosphate, was replaced by Ala or Arg by site-directed mutagenesis. Both mutant enzymes were purified to homogeneity; their absorption spectra indicated that both mutant enzymes contained pyridoxal phosphate bound non-covalently. Even though the standard assay method did not indicate any activity with either mutant, addition of an amino donor, D-alanine, to the Arg-145 mutant enzyme led to a slow decrease in absorption at 392 nm with a concomitant increase in absorption at 333 nm. This result suggests that the enzyme was converted into the pyridoxamine phosphate form. The amount of pyruvate formed was almost equivalent to that of the reactive pyridoxal phosphate in the mutant enzyme. Thus, the Arg-145 mutant enzyme is able to catalyze slowly the half-reaction of transamination. Exogenous amines, such as methylamine, had no effect on the half-reaction with the Arg-145 mutant enzyme. In contrast, the Ala-145 mutant enzyme neither underwent the spectral change by addition of D-alanine nor catalyzed pyruvate formation, in the absence of added amine. However, the Ala-145 mutant enzyme catalyzed the half-reaction significantly in the presence of added amine. These findings suggest that a basic amino acid residue, such as lysine or arginine, is required at position 145 for catalysis of the half-reaction. The role of the exogenous amines differs with various active-site mutant enzymes.

Alanine↗
PubMed1991

Metalloselenonein, the selenium analogue of metallothionein: synthesis and characterization of its complex with copper ions.

We used an automated peptide synthesizer to produce a peptide, metalloselenonein, that contains selenocysteine residues substituted for all cysteine residues in Neurospora crassa copper metallothionein. Metalloselenonein binds 3 mol of Cu(I) per mol. This adduct shows a broad absorption band between 230 and 400 nm and a fluorescence band at 395 nm, which can be attributed to copper-selenolate coordination. The circular dichroism spectrum of the copper-metalloselenonein complex shows a positive band around 245 nm attributable to asymmetry in metal coordination.

Amino Acids↗
PubMed1991

Thermostable aspartate aminotransferase from a thermophilic Bacillus species. Gene cloning, sequence determination, and preliminary x-ray characterization.

The gene encoding aspartate aminotransferase of a thermophilic Bacillus species, YM-2, has been cloned and expressed efficiently in Escherichia coli. The primary structure of the enzyme was deduced from nucleotide sequences of the gene and confirmed mostly by amino acid sequences of tryptic peptides. The gene consists of 1,176 base pairs encoding a protein of 392 amino acid residues; the molecular mass of the enzyme subunit is estimated to be 42,661 daltons. The active site lysyl residue that binds the coenzyme, pyridoxal phosphate, was identified as Lys-239. Comparison of the amino acid sequence with those of aspartate aminotransferases from other organisms revealed very low overall similarities (13-14%) except for the sequence of the extremely thermostable enzyme from Sulfolobus solfataricus (34%). Several amino acid residues conserved in all the compared sequences include those that have been reported to participate in binding of the coenzyme in three-dimensional structures of the vertebrate and E. coli enzymes. However, the strictly conserved arginyl residue that is essential for binding of the distal carboxyl group of substrates is not found in the corresponding region of the sequences of the thermostable enzymes from the Bacillus species and S. solfataricus. The Bacillus aspartate aminotransferase has been purified from the E. coli clone cell extracts on a large scale and crystallized in the buffered ammonium sulfate solution by the hanging drop method. The crystals are monoclinic with unit cell dimensions a = 121.2 A, b = 110.5 A, c = 81.8 A, and beta = 97.6 degrees, belonging to space group C2, and contain two molecules in the asymmetric unit. The crystals of the enzyme-alpha-methylaspartate complex are isomorphous with those without the substrate analog.

Amino Acid Sequence↗