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Title: Phanerochaete chrysosporiumにおける菌糸の発達とペルオキシダーゼ活性の分布
Other Titles: Ultrastructural Changes and Peroxidase Localization with the Development of Phanerochaete chrysosporium Hyphae
Authors: 高部, 圭司  KAKEN_name
北條, 健生  KAKEN_name
斉藤, 奈緒子  KAKEN_name
佐伯, 浩  KAKEN_name
三宅, 繁輝  KAKEN_name
深澤, 和三  KAKEN_name
Author's alias: Takabe, Keiji
Hojo, Takeo
Saito, Naoko
Saiki, Hiroshi
Miyake, Shigeki
Fukazawa, Kazumi
Issue Date: 21-Dec-1992
Publisher: 京都大学農学部附属演習林
Journal title: 京都大学農学部演習林報告
Volume: 64
Start page: 192
End page: 202
Abstract: 白色腐朽菌であるPhanerochaete chrysosporiumの菌糸の発達過程とペルオキシダーゼ活性の局在を電子顕微鏡観察した。菌を液体培地で培養すると, 2日目まではペルオキシダーゼがあまり分泌されなかったが3日目には活発に分泌されるようになった。酵素を分泌する前と分泌中の菌糸の微細構造を急速凍結置換固定 (RFS) 法で観察・比較すると, 幾つかの構造上の変化が認められた。酵素分泌中の菌糸では, 細胞壁が厚みを増し, 内層部は水溶性多糖で充填されていた。細胞内では粗面小胞体や液胞が発達し, 滑面小胞体や起源のわからない小胞, リング状の膜構造物が出現した。一方ペルオキシダーゼ活性は4日目の菌糸の細胞壁内層部, 原形質膜, リング状の膜構造物に局在していた。菌糸細胞壁内層部に認められたペルオキシダーゼは水溶性多糖中に保持されているものと思われる。このことは実際に菌糸が木材細胞壁を腐朽していく時に, 酵素によるリグニン分解を温和に進行させ, リグニン分解派生物の再重合を効果的に防止するものと考えられる。菌糸によるペルオキシダーゼの合成と分泌のメカニズムに関しても電子顕微鏡観察の結果をもとに考察した。
Ultrastructural changes of hyphae in white-rot fungus Phanerochaete chrysosporium were observed after rapid freeze and freeze substitution (RFS). Localization of peroxidase in the hyphae was also observed. Peroxidase activity in the extracellular fluid showed a dramatic increase on 3 'rd day followed by gradual decrease after 5'th day. Ultrastructure of the hyphae on 4 'th day was quite different from that on 2'nd day. The pyphae on 4'th day have thick cell wall composed of outer layer showing fibrillar structure and inner one containing amorphous water-soluble polysaccharide. Rough-endoplasmic reticula and large vacuoles containing electron opaque material appeared in the hyphae on 4'th day. Smooth endoplasmic reticula, many vesicles and the membranes showing ring-like structure were also observed. Peroxidase activity in the hyphae on 4'th day was localized at inner layer of fungal cell wall, plasma membrane and the membrane showing ring-like structure. The enzyme localized at the inner layer may be retained within the amorphous water-soluble polysaccharide. The polysaccharide may immobilize the enzyme on the wood cell walls, when the enzyme is secreted extracellularly. In addition, the presence of the amorphous polysaccharide in the reaction site causes the mild degradation of lignin and prevents the re-polymerization of degraded lignin fragments. Cell organellae involved in biosynthesis and secretion of the enzyme were also discussed.
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