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1Author    Kira Oikawa, Kenkichi Ebisui, Masayuki Sue, Atsushi Ishihara, Hajime IwamuraRequires cookie*
 Title    Purification and Characterization of a ß-Glucosidase Specific for 2,4-Dihydroxy- 7-methoxy-l,4-benzoxazin-3-one (DIM BOA) Glucoside in Maize  
 Abstract    Occurrence and properties of hydroxamic acid glucoside glucosidase were investigated in 10-day-old, autotrophic maize (Zea mays L.) in which 2,4-dihydroxy-7-methoxy-l,4-benzoxazin-3-one glucoside (DIMBOA-G) is a major benzoxazinone component. Crude ex­ tracts of both leaves and roots showed glucosidase activity for both DIMBOA-G and 2,4-dihydroxy-l,4-benzoxazin-3-one glucoside (DIBOA-G). A cation-exchange chromatography after cryoprecipitation of the extract from leaves gave a peak with both activities, and further purification by ion-exchange and hydroxyapatite chromatography gave a fraction with an apparent homogeneity, the purification being 560 fold. The K m values (m M) of the purified glucosidase were 0.16 for DIMBOA-G, 0.68 for DIBOA-G and 2.96 for p-nitrophenyl-ß-D-glucopyranoside. The activity on salicin and esculin was too low to be detected. The data indicate that a glucosidase specific for DIMBOA-G comes into contact with constitutive benzoxazinone glucosides producing defensive aglycone when plants are damaged by micro­ bial or insect attacks. tance of plants to deleterious microbes and insects. The benzoxazinones are also known to catalyti-cally degrade s-triazine herbicides and thus re­ sponsible for their detoxification (Willard and Penner, 1976). Recently, we have found in both wheat and maize that benzoxazinone glucosides occur in a high amount during the stage from germination to autotrophic growth, together with a lesser amount of free aglycones (Nakagawa et al., 1995; Ebisui et al., 1998). As the plants enter into the autotrophic growth stage, the glucosides decrease to a con­ stant, lower level, and the aglycones become bar­ ely detectable. In maize, we have found that a DIM BOA -G specific glucosidase also occurs con­ currently with the transient occurrence of benzo­ xazinones, suggesting that the specific glucosidase plays a role in microbial and insect attacks to pro­ duce defensive aglycones in a high amount during the vulnerable, juvenile stage of growth. In this study, we examined w hether the glucosidase that comes into contact with the glucosides when auto­ trophic tissue is disintegrated is a specific one. 
  Reference    Z. Naturforsch. 54c, 181—185 (1999); received November 19 1998/January 11 1999 
  Published    1999 
  Keywords    Benzoxazinones, Zea mays, Gramineae, ß-Glucosidase 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-0181.pdf 
 Identifier    ZNC-1999-54c-0181 
 Volume    54 
2Author    Achim Hager, Roland Frenzel, D. Orothee LaibleRequires cookie*
 Title    ATP-dependent Proton Transport into Vesicles of Microsomal Membranes of Zea mays Coleoptiles  
 Abstract    ATP-dependent proton pumps were found in the vesicles of microsomal membrane fractions of maize coleoptiles. Two membrane fractions isolated by density gradient centrifugation were identified by the aid of marker enzymes and electron microscopic analysis. Membrane fraction A largely consisted of vesicles of smooth ER and of the Golgi complex, fraction B predominantly of vesicles of plasmalemma and rough ER. The pH-indicator, neutral red, was used to measure changes in pH in the vesicles after ATP addition. Due to the binding of protonated neutral red molecules (NRH+) to negative charges of the energized membrane, a strong metachromasy of NRH+-absorption can be observed. Therefore, in order to accurately measure A pH a pH-dependent change in absorption of neutral red covering the whole NR-spectrum was set up as difference spectra. The commonly employed method of measuring AA of neutral red at just one wavelength (525 nm) leads to entirely incorrect results. It could be demonstrated that the ATP-dependent translocation of H+-ions into the interior of the vesicles was most efficient at pH 7. Acidification, which reaches its maximum 10-15 min after ATP addition, can be reverted by adding CCCP. An ATP-dependent proton-translocation into the vesicles of fraction B was also observed, however, the proton translocation is less than that found in fraction A in relation to the amount of protein found in each. The membrane fraction A displays a strong oxidation of NADH subsequently followed by an alkalization of the medium. This process cannot be reverted by adding CCCP. NADH oxidation at membranes of fraction A is consequently not an integral part of a redox-pump. A possible significance of the ATP-dependent proton pump in membranes of the ER and Golgi fraction of coleoptiles is discussed in connection with auxin induced elongation growth. 
  Reference    Z. Naturforsch. 35c, 783—793 (1980); received May 22 1980 
  Published    1980 
  Keywords    Proton Pump, H+-ATPase, Zea mays, Coleoptile, Auxin 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0783.pdf 
 Identifier    ZNC-1980-35c-0783 
 Volume    35 
3Author    A. Hager, P. HermsdorfRequires cookie*
 Title    A H +/Ca2+ Antiporter in Membranes of Microsomal Vesicles from Maize Coleoptiles, a Secondary Energized Ca2+ Pump  
 Abstract    Microsomal vesicles prepared from the ER and the Golgi apparatus o f maize coleoptiles possess an ATP-fueled, Cl_-dependent proton pump which can cause an intravesicular acidifica­ tion of the vesicles (A. Hager. This acidification is very specifically inhibited by Ca2+. The inhibition is already distinct at concentrations o f 30 hm. While 10-fold higher concentrations of La3+ produce similar effects, Mg2+ remains ineffective even at very high concentrations. If Ca2+ is added after acidification o f the vesicles, a rapid H +-efflux proportional to the amount of Ca2+ added characterizes the first reaction phase. In the second reaction phase acidification within the vesicles commences anew, however, at a reduced rate. If Ca2+ is added to vesicles whose proton pump has been inhibited by DCCD, the first reaction phase remains unchanged, while the acidification in the second reaction phase does not set in, and only a leak out o f protons is observed. These results give support for a H +/C a2+-antiporter mechanism which can function as a secondary energized Ca2+-pump and regulate the Ca2+-concentration in the cytoplasm. 
  Reference    Z. Naturforsch. 36c, 1009—1012 (1981); received September 2 1981 
  Published    1981 
  Keywords    Ca2+ Pump, H+-ATPase, Membrane Vesicles, Coleoptile, Zea mays 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-1009.pdf 
 Identifier    ZNC-1981-36c-1009 
 Volume    36 
4Author    A. Hager, W. BiberRequires cookie*
 Title    Functional and Regulatory Properties of H + Pumps at the Tonoplast and Plasma Membranes of Zea mays Coleoptiles  
 Abstract    A microsomal membrane fraction (6000 x g supernatant of a cell homogenate), isolated from coleoptiles of Zea mays, was separated by isopycnic sucrose density gradient centrifugation in the presence of EDTA and without a prior pelleting step to avoid irreversible sticking of different membrane species. The membrane fractions were characterized by assaying commonly used marker enzymes, and the levels of activity investigated of ATP hydrolysis, ATP-dependent H+ transport, and co-and countertransport o f ions, such as Cl-, fumarate2-, K+ and Li+. The following results were obtained: 
  Reference    Z. Naturforsch. 39c, 927—937 (1984); received August 6 1984 
  Published    1984 
  Keywords    ATPase, H+-Pumping, Ion Transport, Coleoptile, Zea mays 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0927.pdf 
 Identifier    ZNC-1984-39c-0927 
 Volume    39