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  • 1
    ISSN: 1432-072X
    Keywords: Poly-β-hydroxybutyrate ; PHB ; Acetoacetyl CoA reductase ; Zoogloea ramigera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Zoogloea ramigera I-16-M was found to contain two stereospecific acetoacetyl CoA reductases; one was NADP+-linked and d(-)-β-hydroxybutyryl CoA specific and the other was NAD+-linked and l(+)-isomer specific. The NADP+-linked enzyme, purified approximately 150-fold, had a pH optimum for the reduction of acetoacetyl CoA at 8.1, but no definite pH optimum for the oxidation of β-hydroxybutyryl CoA. The apparent Michaelis constants for acetoacetyl CoA and NADPH were 8.3 and 21 μM, respectively. The enzyme was markedly inhibited by acetoacetyl CoA at concentrations higher than 10 μM. The incorporation of [1-14C]acetyl CoA into poly-β-hydroxybutyrate (PHB) by bacterial crude extract (containing β-ketothiolase, acetoacetyl CoA reductases, enoyl CoA hydratases and PHB synthases) or by a system reconstituted from purified preparations of β-ketothiolase, acetoacetyl CoA reductase and PHB synthase, was observed only in the presence of NADPH, but not NADH. Among various enzymes involved in PHB metabolism, only the specific activity of glucose 6-phosphate dehydrogenase was elevated 5-fold within 2 h after the addition of glucose to the cells grown in the basal medium. These findings suggest that, in Z. ramigera I-16-M, acetoacetyl CoA is directly reduced to d(-)-β-hydroxybutyryl CoA by the NADP+-dependent reductase, and PHB synthesis is at least partially controled by NADPH availability through glucose 6-phosphate dehydrogenase.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-2568
    Keywords: HELICOBACTER PYLORI ; HAMARTOMATOUS FUNDIC POLYP ; ADHERENCE ; IgA ; LEWIS B ANTIGEN
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Helicobacter pylori infection of the gastricmucosal surface was investigated in patients withhamartomatous fundic polyps or hyperplastic polyps andin patients without endoscopic evidence of disease(healthy subjects). Presence of H. pylori infection wasdetermined by culture, histologic examination, and theendoscopic phenol red test. Adherence of H. pylori wasevaluated with scanning electron microscopic examination of antral biopsy specimens. Bothprevalence of H. pylori infection (P 〈 0.001) and H.pylori adherence (P 〈 0.05) were less in patientswith hamartomatous fundic polyps than in healthy subjects and patients with hyperplastic polyps.However, the percentages of plasma cells in gastricmucosa that contained IgA and of gastric epithelialcells that expressed Lewis b did not differsignificantly among the three groups. These findings suggestthat defense mechanisms against the attachment of H.pylori other than IgA or Lewis b antigen are present inpatients with hamartomarous fundic polyps.
    Type of Medium: Electronic Resource
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