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1999 (1)
1978 (1)
1Author    Siegrid Schoch, Wolfram SchäferRequires cookie*
 Title    Tetrahydrogeranylgeraniol, a Precursor of Phytol in the Biosynthesis of Chlorophyll a — Localization of the Double Bonds  
 Abstract    Pheophytins esterified with phytol and tetrahydrogeranylgeraniol are isolated from etiolated oat seedlings after short (1 min) exposure to light and a subsequent dark period of 15 to 20 min. After saponification of the pheophytins, a mixture of the alcohols was isolated. The structure of tetra­ hydrogeranylgeraniol was established as 3,7,11,15-tetramethyl-zl2'14 hexadecadiene-l-ol (3a). The implications for chlorophyll biosynthesis are discussed. 
  Reference    Z. Naturforsch. 33c, 408—412 (1978); received March 23 1978 
  Published    1978 
  Keywords    Birthday Avena sativa, Gramineae, Oats, Chlorophyll Biosynthesis, Phytol 
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 TEI-XML for    default:Reihe_C/33/ZNC-1978-33c-0408.pdf 
 Identifier    ZNC-1978-33c-0408 
 Volume    33 
2Author    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