Biomedical subjects

J Katsuwon

Publications and source records attributed to J Katsuwon.

5 recordsLinked to original sources

PubMed2001

An empirical approach for estimating the equivalent chain length of fatty acid methyl esters in multistep temperature-programmed gas chromatography.

The equivalent chain length (ECL) has been widely accepted as an identification tool for fatty acid methyl esters (FAMEs). In this study, FAMEs from the seed oil of Chinese mustard (Brassica juncea) analyzed on a 0.25-mm-i.d. capillary column coated with an SA-WAX are used as an example for the calculation of the ECL in single-, two-, three-, and four-step temperature-programmed gas chromatography. The ECLs of unsaturated FAMEs tend to increase with temperature, and they agree well with those reported in the literature.

Chromatography, Gas↗

PubMed1993

Superoxide dismutase activity in root-colonizing pseudomonads.

Several saprophytic fluorescent pseudomonads that are aggressive root colonizers express similar specific activities of superoxide dismutase during growth in liquid culture. The pseudomonads have the potential to produce hydrogen peroxide sensitive and hydrogen peroxide insensitive isoforms of superoxide dismutase with distinct mobilities in nondenaturing polyacrylamide gel electrophoresis. Synthesis of the hydrogen peroxide insensitive form is enhanced by limited iron availability, by exposure to Mn2+, and to a lesser extent by external sources of superoxide anion. Unlike Pseudomonas aeruginosa, a root-colonizing strain of Pseudomonas putida did not show regulation of isoform pattern by phosphate availability. A plasmid potentially encoding the pseudomonad hydrogen peroxide sensitive form complemented the superoxide dismutase deficiency in a mutant of Escherichia coli lacking expression of both Fe and Mn genes. Contact between the plant root and pseudomonad or E. coli cells that lack or express superoxide dismutase did not influence superoxide anion production from root surface enzymes. The pseudomonad and the superoxide dismutase deficient and producing E. coli strains survived exposure to the root equally well. Only the hydrogen peroxide sensitive isoform of superoxide dismutase was detected in P. putida cells associated with bean root surfaces.

Cloning, Molecular↗

PubMed1990

Catalase and superoxide dismutase of root-colonizing saprophytic fluorescent pseudomonads.

Root-colonizing, saprophytic fluorescent pseudomonads of the Pseudomonas putida-P. fluorescens group express similar levels of catalase and superoxide dismutase activities during growth on a sucrose- and amino acid-rich medium. Increased specific activities of catalase but not superoxide dismutase were observed during growth of these bacteria on components washed from root surfaces. The specific activities of both enzymes were also regulated during contact of these bacteria with intact bean roots. Increased superoxide dismutase and decreased catalase activities were observed rapidly, by 10 min upon inoculation of cells onto intact bean roots. Catalase specific activity increased with time to peak at 12 h before declining. By 48 h, the cells displayed this low catalase but maintained high superoxide dismutase specific activities. Catalase with a low specific activity and a high superoxide dismutase activity also were present in extracts of cells obtained from 7-day-old roots colonized from inoculum applied to seed. This specific activity of superoxide dismutase of root-contacted cells was about fourfold-higher in comparison to cells grown on rich medium, whereas the specific activity for catalase was reduced about fivefold. A single catalase isozyme, isozyme A, and one isozyme of superoxide dismutase, isozyme 1, were detected during growth of the bacteria on root surface components and during exposure of cells to intact bean roots for 1 h. An additional catalase, isozyme B, was detected from bacteria after exposure to the intact bean roots for 12 h. Catalase isozyme A and superoxide dismutase isozyme 1 were located in the cytoplasm and catalase band B was located in the membrane of P. putida.

Journal Article↗

PubMed1989

Response of plant-colonizing pseudomonads to hydrogen peroxide.

Colonization of plant root surfaces by Pseudomonas putida may require mechanisms that protect this bacterium against superoxide anion and hydrogen peroxide produced by the root. Catalase and superoxide dismutase may be important in this bacterial defense system. Stationary-phase cells of P. putida were not killed by hydrogen peroxide (H(2)O(2)) at concentrations up to 10 mM, and extracts from these cells possessed three isozymic bands (A, B, and C) of catalase activity in native polyacrylamide gel electrophoresis. Logarithmic-phase cells exposed directly to hydrogen peroxide concentrations above 1 mM were killed. Extracts of logarithmic-phase cells displayed only band A catalase activity. Protection against 5 mM H(2)O(2) was apparent after previous exposure of the logarithmic-phase cells to nonlethal concentrations (30 to 300 muM) of H(2)O(2). Extracts of these protected cells possessed enhanced catalase activity of band A and small amounts of bands B and C. A single form of superoxide dismutase and isoforms of catalase were apparent in extracts from a foliar intercellular pathogen, Pseudomonas syringae pv. phaseolicola. The mobilities of these P. syringae enzymes were distinct from those of enzymes in P. putida extracts.

Journal Article↗

PubMedDate not supplied

Cloning, characterization and phenotypic expression in Escherichia coli of catF, which encodes the catalytic subunit of catalase isozyme CatF of Pseudomonas syringae.

The phytophathogenic, gram-negative bacterium Pseudomonas syringae pv. syringae 61 contains three isozymes of catalase (EC 1.11.1.6), which have been proposed to play a role in the bacterium's responses to various environmental stresses. To study the role of individual isozymes, the gene coding for the catalytic subunit of one catalase isozyme was cloned from a cosmid library hosted in Escherichia coli DH5 alpha by using a designed catalase-specific DNA probe for the screening. One out of four clones with a catalase-positive genotype was subcloned and a pUC19-based 2.7 x 10(3)-base (2.7-kb) insert subclone, pMK3E5, was used to transform catalase-deficient E. coli strain UM255 (HPI-, HPII-). The transformants contained a single isozyme of catalase that had electrophoretic and enzymic properties similar to catalase isozyme CatF from P. syringae pv. syringae 61. Analysis of the sequenced 2.7-kb insert DNA revealed six putative open-reading frames (ORF). The 1542-base-pair DNA sequence of ORF2, called catF, encodes a peptide of 513 amino acid residues with a calculated molecular mass of 66.6 kDa. The amino acid sequence deduced from catF had homology to the primary structure of true catalases from mammals, plants, yeasts and bacteria. The activity of the recombinant catalase was inhibited by 3-amino-1,2,4-triazole and azide and stimulated by chloramphenicol. The N terminus contained a signal sequence of 26 amino acids necessary for secretion into the periplasm, a so-far unique property of Pseudomonas catalases.

Amino Acid Sequence↗