Metabolic products of microorganisms 181. Chitin synthase from fungi,a test model for substances with insecticidal properties

Chitin synthase from Coprinus cinereus (Schaeff. ex Fr.) S. F. Gray (= C. lagopus sensu Buller) was used as a model for chitin synthase from insects. The effect of dimilin (difluorobenzuron), captan (trichloromethylsulfonyl fungicide), kitazin P (organophosphorus ester fungicide) and parathion (organophosphorus insecticide) on the fungal enzyme was compared with the effect of nikkomycin (nucleoside-peptide antibiotic).Metabolic products of microorganisms. 180. M. Brufani, L. Celai, W. Keller-Schierlein, E. Pretsch: Revised structure of naphthomycin. J. Antibiot. (Tokyo) (in press)     

Peroxidase-benzhydroxamic acid complexes: spectroscopic evidence that a Fe-H2O distance of 2.6 Å can correspond to hexa-coordinate high-spin heme

Resonance Raman (RR) spectra have been obtained for single-crystal horseradish peroxidase isozyme C complexed with benzhydroxamic acid (BHA). The data are compared with those obtained in solution by both RR and electronic absorption spectroscopies at room and low (12-80 K) temperatures. Moreover, the analysis has been extended to Coprinus cinereus peroxidase complexed with BHA. The results obtained for the two complexes are very similar and are consistent with the presence of an aqua six-coordinate high-spin heme. Therefore it can be concluded that despite the rather long Fe-H2O distance of 2.6-2.7 A found by X-ray crystallography in both complexes, the distal water molecule can still coordinate to the heme iron.     

Enzymatic synthesis and curing of polycardol from renewable resources

For the first time, oxidative polymerization of cardol derived from cashew nut shell liquid (CNSL), which is a cheap, useful, and renewable substance, has been carried out using a fungal peroxidase from Coprinus cinereus (CiP). Cardol, one of the major components of CNSL, is a resorcinol derivative mainly having a C15 unsaturated hydrocarbon chain with 1–3 double bonds at a meta position. To date cardol has not been completely exploited as a monomer for enzymatic polymerization. Enzymatic polymerization of cardol proceeded with higher yield in an equivolume mixture of tert-butanol and phosphate buffer (pH 7.0). The yield and molecular weight of polycardol depended on the hydrogen peroxide concentration. Polycardol was rapidly cured at room temperature within 4 h to give harden dry and dark brown color coatings. Pencil scratch hardness data indicated that the curing rate of polycardol was superior to those of polycardanol. Thermogravimetric analysis implied that the cured product from polycardol was thermally more stable than that from polycardanol. We expect that polycardol from renewable resources, which is similar to or superior to polycardanol, can find many applications in the near future.     

Ultrastructural Study of Secondary Wall Formation in the Stem Fiber of Phyllostachys pubescens

Ultrastructural changes in secondary wall formation of Phyllostachys pubescens Mazel fiber were investigated with transmission electron microscopy. Fiber developed initially with the elongation of cells containing ribosomes, mitochondria and Golgi bodies in the dense cytoplasm. During the wall thickening, the number of rough endoplasmic reticulum and Golgi bodies increased apparently. There were two kinds of Golgi vesicles, together with the ones from endoplasmic reticulum formed transport vesicles. Many microtubules were arranged parallel to the long axis of the cell adjacent to the plasmalemma. Along with the further development of fiber, polylamellate structure of the secondary wall appeared, with concurrent agglutination of chromatin in the nucleus, swelling and disintegration of organelles, while cortical microtubules were still arranged neatly against the inner side of plasmalemma. Lomasomes could be observed between the wall and plasmalemma. The results indicated that the organelles, such as Golgi bodies together with small vesicles, rough endoplasmic reticulum and lomasomes, played the key role in the thickening and lignification of the secondary wall of bamboo fiber, though cortical microtubules were correlative with the process as well.     

Ultrastructure and evolution of ballistosporic basidiospores

Basidiospores oiCoprinus cinereus were examined before and during spore discharge using light microscopy, and SEM of frozen-hydrated and other preparations. The process of droplet development at the hilar appendix was divided into three stages: pre-droplet, early and late enlargement. The fully expanded droplet was preserved only in frozen-hydrated specimens. Two-step droplet enlargement was also observed with TEM in Boletus rubinellus, and the droplet at the early enlargement stage was enclosed by a trilaminate membrane. The droplet was not observed in Auricularia species, but basidiospore preservation for SEM was optimum in Auricularia auricula with frozen-hydrated preparations. The hilar appendix of Auricularia fuscosuccinea as studied by TEM was simple compared with those of the Homobasidiomycetes. The implications of the data for evolution of the ballistosporic basidiospore and the discharge mechanism are considered.     

Phospholipid-enzyme interactions of chitin synthase of Coprinus cinereus

Abstract The effect of phospholipids on chitin synthase activity has been studied with digitonin-solubilized and partially purified preparations from Coprinus cinereus . When cholate was used as detergent, it inhibited enzyme activity, but this inhibition was reversed by increasing concentrations of phospholipids. Preincubation with cholate and phospholipid caused irreversible loss of activity. When sonicated with solubilized enzyme preparation, dimyristoyl phosphatidyl choline strongly stimulated activity, while dioleoyl phosphatidyl choline was inhibitory. The Arrhenius plot of the effect of temperature on enzyme activity contained breaks, characteristic of a membrane-bound enzyme. It is suggested that chitin synthase requires an annulus of phospholipids for activity.