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K Soda

Publications and source records attributed to K Soda.

At least 253 records · Page 14Linked to original sources
PubMed1986

Purification and characterization of yeast L-kynurenine aminotransferase with broad substrate specificity.

L-Kynurenine aminotransferase [L-kynurenine:2-oxoglutarate aminotransferase (cyclizing), EC 2.6.1.7] has been purified to homogeneity and crystallized from cell-free extracts of a yeast, Hansenula schneggii, grown in a medium containing L-tryptophan as an inducer. The enzyme has a molecular weight of about 100,000 and consists of two subunits identical in molecular weight (52,000). The enzyme exhibits absorption maxima at 280, 335, and 430 nm, and contains 2 mol of pyridoxal 5'-phosphate per mol of enzyme. The enzyme-bound pyridoxal 5'-phosphate shows negative circular dichroic extrema, in contrast with other pyridoxal 5'-phosphate acting on L-amino acids. In addition to L-kynurenine and alpha-ketoglutarate, which are the most preferred substrates, a large number of L-amino acids and alpha-keto acids can serve as substrates; the extremely broad substrate specificity is the most characteristic feature of this yeast enzyme. The enzyme activity is significantly affected by both carbonyl and sulfhydryl reagents. Certain dicarboxylic acids such as adipate and pimelate act as competitive inhibitors. Addition of various substrate amino acids to the culture medium results in the inductive formation of aminotransferases which are immunochemically indistinguishable from L-kynurenine aminotransferase.

Amino Acids↗
PubMed1986

Different classes of antibody activities to Trichosporon cutaneum antigen in summer-type hypersensitivity pneumonitis by enzyme-linked immunosorbent assay.

To assess the diagnostic value of antibody activities to Trichosporon cutaneum antigen in patients with summer-type hypersensitivity pneumonitis in Japan, we measured the serum IgG, IgA, and IgM antibodies to saline-soluble antigen of homogenized T. cutaneum cells by enzyme-linked immunosorbent assay (ELISA). The IgG antibody activity was observed in serum samples from 25 (83%) of the 30 patients and in 9 (82%) of the 11 asymptomatic family members. The IgA antibody activity was found in 25 (83%) of the patients but in only 3 (27%) of asymptomatic family members. Unexpectedly, we found no significant correlation between the IgG and IgA antibody activities to the same antigen in individual patients. Moreover, although the IgG antibody activity was related to the precipitating antibody, the IgA antibody activity was not. The IgM antibody activity by ELISA was found in only 5 (17%) of the patients. The IgG+IgA+IgM antibody activity was demonstrated in 27 (90%) of the 30 patients, and of 3 serum samples that were found negative by the ELISA method, 2 were positive by the IFA method. We conclude that the detection of the serum IgG and IgA antibody activities to T. cutaneum antigen by ELISA is a simple and useful serodiagnostic test for summer-type hypersensitivity pneumonitis. Measurement of the IgA antibody activity is especially helpful in discriminating symptomatic from asymptomatic family members.

Alveolitis, Extrinsic Allergic↗
PubMed1986

Specific bronchoalveolar lavage IgA antibody in patients with summer-type hypersensitivity pneumonitis induced by Trichosporon cutaneum.

Patients with summer-type hypersensitivity pneumonitis induced by Trichosporon cutaneum were studied with respect to specific IgG, IgA, and secretory IgA (S-IgA) antibody activities to T. cutaneum in serum and bronchoalveolar lavage fluid (BALF). A strain of T. cutaneum was isolated from 1 patient's pillow. All serum samples from the family members (2 patients and 2 asymptomatic) contained IgG antibody activity to T. cutaneum, and the titers showed no difference between the patients and asymptomatic family members. On the other hand, IgA and S-IgA antibody activities in serum and BALF were markedly increased only in the patients, and the titers were well correlated with the clinical course. The BALF/serum ratio of specific antibody activity was markedly elevated in IgA and S-IgA antibody activities in striking contrast to that in IgG, suggesting an immune reaction of the respiratory tract. The bronchial challenge test with T. cutaneum antigen was positive in the patients, but not in an asymptomatic family member. These results indicate that measurement of IgA and S-IgA antibody activities in serum and BALF is useful for diagnosis and evaluation of disease activity in summer-type hypersensitivity pneumonitis.

Adult↗
PubMed1986

Mechanism of hematuria. I. Electron microscopic demonstration of the passage of a red blood cell through a glomerular capillary wall in rat masugi nephritis.

Masugi nephritis was induced in Sprague-Dawley rats by an intravenous injection of rabbit anti-rat kidney serum. In the autologous phase of the disease, three of 18 rats manifested continuous hematuria. Ultrastructural examination of renal glomeruli by transmission and scanning microscopy revealed gaps in the basement membranes, and the transcapillary passage of red blood cells through the discontinuous regions in the hematuric rats. Control animals revealed no gaps in the glomerular basement membranes regardless of the method used in their preparation for electron microscopy. These data support the hypothesis that hematuria is a result of the passage of red blood cells through gaps in the glomerular basement membrane in Masugi nephritis.

Animals↗
PubMed1985

Synthesis of L-selenodjenkolate and its degradation with methionine gamma-lyase.

A convenient method for the synthesis of a new selenium-containing amino acid, L-selenodjenkolate (3,3'-methylenediselenobis(2-aminopropionic acid)), is described. The starting material, selenocystine, was found to be prepared easily from commercially available beta-chloro-L-alanine, elemental selenium, and sodium borohydride. These synthetic procedures are useful for the preparation of the isotope-labeled compounds. The physiochemical properties of selenodjenkolate thus prepared are reported. This amino acid undergoes alpha, beta-elimination to produce pyruvate, formaldehyde, ammonia, and selenium by bacterial methionine gamma-lyase under aerobic conditions: the Vmax and Km values were determined to be 0.5 mumol/min/mg and 2.3 mM, respectively.

Alanine↗
PubMed1985

1H NMR studies of substrate hydrogen exchange reactions catalyzed by L-methionine gamma-lyase.

Hydrogen exchange reactions of various L-amino acids catalyzed by L-methionine gamma-lyase (EC 4.4.1.11) have been studied. The enzyme catalyzes the rapid exchange of the alpha- and beta-hydrogens of L-methionine and S-methyl-L-cysteine with deuterium from the solvent. The rate of alpha-hydrogen exchange was about 40 times faster than that of the enzymatic elimination reaction of the sulfur-containing amino acids. The enzyme also catalyzes the exchange reaction of alpha- and beta-hydrogens of the following straight-chain L-amino acids which are not susceptible to elimination: norleucine, norvaline, alpha-aminobutyrate, and alanine. The exchange rates of the alpha-hydrogen and the total beta-hydrogens of L-alanine and L-alpha-aminobutyrate with deuterium followed first-order kinetics. For L-norvaline, L-norleucine, S-methyl-L-cysteine, and L-methionine, the rate of alpha-hydrogen exchange followed first-order kinetics, but the rate of total beta-hydrogen exchange decreased due to a primary isotope effect at the alpha-position. One beta-hydrogen of S-methyl-L-cysteine was exchanged faster than the other, although both the beta-hydrogens were exchanged completely with deuterium ultimately. L-Phenylalanine and L-tryptophan slowly underwent alpha-hydrogen exchange. The pro-R hydrogen of glycine was deuterated stereospecifically. None of the following amino acids were susceptible to the enzymatic hydrogen exchange: D isomers of the above amino acids, branched chain L-amino acids, acidic L-amino acids, and basic L-amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon-Sulfur Lyases↗
PubMed1985

Stereochemistry of the kynureninase reaction.

The steric course of the replacement of the anthranilyl group of kynurenine by hydrogen was determined by conversion of (2S,3R)- and (2S,3S)-[3-3H]kynurenine into alanine with kynureninase in D2O, followed by chirality analysis of the alanine methyl group. To minimize enolization, the labeled substrates were generated in situ from the corresponding stereospecifically tritiated tryptophan species. The result, replacement in a retention mode, together with the finding that tritium from the alpha-position of the substrate is recycled and appears both at C alpha and C beta of the product suggests a single base mechanism and an active site geometry of the pyridoxal phosphate-substrate complex in which H alpha and the beta-substituent are syn oriented.

Chemical Phenomena↗
PubMed1985

Mechanism of reactions catalyzed by selenocysteine beta-lyase.

The reaction mechanism of selenocystine beta-lyase has been studied and it was found that elemental selenium is released enzymatically from selenocysteine, and reduced to H2Se nonenzymatically with dithiothreitol or some other reductants that are added to prepare selenocysteine from selenocystine in the anaerobic reaction system. 1H and 13C NMR spectra of L-alanine formed in 2H2O have shown that an equimolar amount of [beta-2H1]- and [beta-2H2]alanines are produced. The deuterium isotope effect at the alpha position was observed; kH/kD = 2.4. These results indicated that the alpha hydrogen of selenocysteine was removed by a base at the active site, and was incorporated into the alpha position of alanine, a product, without exchange of a solvent deuterium. When the enzyme was incubated with L-selenocysteine in the absence of added pyridoxal 5'-phosphate, the activity decreased with prolonged incubation time. However, the activity was recovered by addition of 5'-phosphate. The spectrophotometric study showed that the inactivated enzyme was the apo form. The apoenzyme was activated by a combination of pyridoxamine 5'-phosphate and various alpha-keto acids such as alpha-ketoglutarate and pyruvate. Thus, the enzyme is inactivated through transamination between selenocysteine and the bound pyridoxal 5'-phosphate to produce pyridoxamine 5'-phosphate and a keto acid derived from selenocysteine. The pyridoxal enzyme, an active form, is regenerated by addition of alpha-keto acids. This regulatory mechanism is analogous to those of aspartate beta-decarboxylase [EC 4.1.1.12], arginine racemase [EC 5.1.1.9], and kynureninase [EC 3.7.1.3] [K. Soda and K. Tanizawa (1979) Adv. Enzymol. 49, 1].

Alanine↗