Changes in the Content of Starch and Activities of some Enzymes of Carbohydrate Metabolism in Cotyledons of Germinating Seeds of Voandzeia subterranea

During the germination of the seeds of Voandzeia subterraneaL. Thouars, the content of starch in the cotyledons fell progressively.There was a substantial increase in amylase activity duringthe first 4 d. The activity of starch phosphorylase increasedafter 6 d when there was a rapid decline in amylase activity.The activities of hexokinase, glucose-6-phosphate dehydrogenase,and 6-phosphogluconate dehydrogenase increased, suggesting thepresence of an active phosphogluconate pathway in the cotyledons.     

Cellulolytic Activities of Botryodiplodia theobromae Pat

Botryodiplodia theobromae Pat., a ‘stain’ fungusisolated from stained and decaying wood of Bombax buonopozenseP. Beauv., attacked isolated blocks of Bombax wood. In theseit perforated the cell walls and formed elongated cavities withpointed ends, usually in chains, in the secondary wall. Thefungus attacked cellulose in a similar manner to soft rot fungi.It used starch and other saccharides present in the wood ofBombax buonopozense as initial substrates before degrading thecellulose and hemicellulose components of the wood. It did notdegrade the lignin component of the wood. Cellulase, ß-glucosidase, and amylase activities weredetected in culture filtrates of Botryodiplodia theobromae.Cellulase synthesis was delayed when the wood powder in themedium contained starch and saccharides. Amylase, too, behavedlike an inducible enzyme and disappeared from the cultures onexhaustion of starch. Electron microscopy showed that cellulose extracted from thewood of Bombax buonopozense was fragmented into small particleson treatment with the culture filtrates of Botryodiplodia theobromae.Cellobiose, glucose, and another saccharide, probably cellotriose,were identified as the products of enzymatic hydrolysis of cellulose. These results are discussed in relation to the attack and degradationof the wood of Bombax buonopozense by Botryodiplodia theobromaein nature.     

Production of Cellulolytic Enzymes by Botryodiplodia theobromae, Pat.

Carboxymethylcellulase (CM-cellulase) and ß-glucosidaseactivities were induced in cultures of Botryodiplodia theobromae,Pat. Both growth of the fungus and CM-cellulase production werebetter with sodium nitrate as nitrogen source than with eitherammonium nitrate or ammonium chloride. Growth, per unit nitrogensupplied, was greater with glutamic acid and aspartic acid asnitrogen sources than with sodium nitrate; this was probablybecause the fungus utilized the carbon of these amino-acids.Most ß-glucosidase activity was formed with ammoniumchloride or ammonium nitrate as nitrogen source. Glucose inhibited the activity of ß-glucosidase markedly.Low glucose concentration (c. 0.003 M) stimulated CM-cellulaseactivity but concentrations above 0.05 M inhibited. The formationof both enzymic activities was repressed in the presence ofglucose. ß-glucosidase activity was more thermolabilethan that of CM-cellulase.     

Cellulase and ({beta}-Glucosidase Components in Culture Filtrates from Botryodiplodia theobromae Pat.

Cellulase and ß-glucosidase components in culturefiltrates from Botryodiplodia theobromaePat. were separatedby polyacrylamide-gel electrophoresis and gel-filtration onSephadex. A correlation between the electrophoretic mobilitiesand gel-filtration behaviour of the components was established.Four cellulase components (Ca, Cb, Cc, and Cd) were recognized with approximate molecular weights of 162 000 (Ca), 15 000(Cb), 10 000 (Cc), and 4500 (Cd). Four ß-glucosidasecomponents (Ba, Bb, Bc, and Bd) were also recognized with molecularweights of 112 000 (Ba), 56 000 (Bb), 27 000 (Be), and 13 300(Bd). The cellulase components appeared to be composed of aggregatesof similar subunits. Similarly, the ß-glucosidasecomponents appeared to be aggregates of similar subunits. Similarly,the ß-glucosidase components appeared to be aggregratesof a subunit that differed from the cellulase subunit. The activitiesof the cellulase components differed on different cellulosicsubstrates. Cotton flock was readily solubilized by a mixtureof cellulase components Ca, Cb, and Cc, an effect which wasenhanced in the presence of component Cd. Any appreciable solubilizationof native cotton fibres required component Ca or, more effectively,Cd.